The sinking of the ‘Bayesian’: A high-stakes gamble over design flaws or crew error

A BBC documentary has reignited the debate: “Millionaire Superyacht: Why Ships Sink” – broadcast on BBC Two at the end of June and available only to viewers in the United Kingdom – addresses the questions that have been occupying two investigative bodies for almost two years: What really caused the “Bayesian” to sink? Almost two years after the sailing yacht sank off the coast of Sicily, there are two fundamentally different explanations for the disaster. Whilst the British safety authority, the MAIB, has identified design flaws as the root cause, the Italian public prosecutor’s office considers the weather to be controllable and accuses the crew. In the background, the luxury shipyard is pursuing a multi-million claim against the widow of the main victim – and has a significant financial stake in the outcome of the investigation.

​The disaster

During the night of 18–19 August 2024, the 56-metre sailing yacht “Bayesian” sank off the coast of Sicily. Seven people lost their lives, including the British tech billionaire Mike Lynch and his 18-year-old daughter Hannah. Fifteen people survived, including Lynch’s wife, Angela Bacares.

On the evening of 18 August, the yacht had anchored in Porticello with 22 people on board – twelve guests and ten crew members – to seek shelter from the forecast storm. The weather was calm at first. Around midnight, the last guest went to bed and two crew members took over the watch. Shortly before four o’clock, the wind suddenly picked up, and both moored yachts – the ‘Bayesian’ and the neighbouring ‘Sir Robert Baden Powell’ – drifted from their moorings. The captain prepared to turn the ship into the wind.

At 4.06 am, the “Bayesian” heeled over 90 degrees to starboard in less than 15 seconds. The generators shut down immediately. Water did not flood in through ventilation openings or open hatches, but poured directly over the starboard railings and from there into the interior via the stairwells. One crew member was thrown overboard, and several people were injured. At 4.22 am, the crew managed to launch a liferaft amidst the chaos. At around 4.45 am, the ship finally sank to a depth of around 50 metres.

The neighbouring “Sir Robert Baden Powell” picked up the distress calls and rescued the survivors. Six passengers and one crew member were recovered, but were already dead.

Why two studies?

Since the sinking, both the British Marine Accident Investigation Branch (MAIB) and the Italian public prosecutor’s office in Termini Imerese, a small town on the north coast of Sicily, have been investigating the causes. These parallel investigations stem from the specific legal situation: the ‘Bayesian’ sank in Italian waters but was registered under the British flag. Consequently, both British and Italian authorities have a legitimate interest in getting to the bottom of the matter – albeit with fundamentally different objectives.

The British MAIB is conducting a safety investigation only. Its statutory remit is expressly not to determine fault or liability, but to prevent future accidents – comparable to the German Federal Bureau of Maritime Accident Investigation (BSU). The Italian public prosecutor’s office, on the other hand, is conducting a criminal investigation: it is examining whether individuals or legal entities can be held criminally liable for the deaths and the loss of the vessel. A criminal classification of the events would have far-reaching consequences – it could serve as the basis for civil claims for damages running into millions.

The MAIB Interim Report: Stability defects as the core problem

In May 2025, the MAIB published its interim report – explicitly stated as a preliminary assessment based on the available documents, as the wreck had not yet been recovered at that time. The findings are nonetheless alarming.

A key element of the investigation was the yacht’s Stability Information Book (SIB) – a mandatory document approved by the flag state that defines the vessel’s operational limits. It contains so-called GZ curves – named after the centre of gravity G and the point of application of the buoyancy force Z – which specify, for various loading conditions, how much a vessel can heel before it is no longer able to right itself. The ‘Bayesian’s’ SIB contained such curves exclusively for sailing with the keel lowered – with documented angles of immersion between 84.3 and 92.3 degrees. What was missing: stability curves for motor operation with the keel raised – in other words, precisely the configuration in force on the night of the accident.

The Wolfson Unit at the University of Southampton calculated an angle of immersion of just 70.6 degrees for this assumed operating condition at the time of the sinking – significantly less than the values documented in the SIB. According to the calculations, the 72-metre-high mast alone was responsible for 50 per cent of the total wind heeling moment. A crosswind gust of just 53.2 to 63.4 knots would have been enough to capsize the ship – possibly even less. The skipper and crew could not have known about this critical threshold: the Stability Information Book was silent on precisely this point.

How much of a factor was the weather?

The UK’s Met Office analysed the satellite data from the night of the accident and identified a mesocyclonic storm front with the characteristics of a supercell, capable of generating surface winds of more than 87 knots.

However, the MAIB report itself puts the significance of the extreme weather into perspective. The stability study carried out by the Wolfson Unit shows that even a continuous crosswind of between 37.6 and 44.8 knots caused the “Bayesian” to heel to a critical angle – without any gusts. On the night of the accident, winds of 41 knots were recorded at the weather station some eight kilometres away. This falls right within this critical range. With the gusts typical of a thunderstorm exceeding this, capsizing was possible even without a supercell. According to the investigations, the structural weakness of the ‘Bayesian’ was so severe that even a severe, but not exceptional, thunderstorm would have been sufficient to cause it to capsize.

The Italian public prosecutor’s office: Is the crew to blame?

In the spring of 2026, the public prosecutor’s office in Termini Imerese put forward a fundamentally different perspective. A meteorological report commissioned by her classifies the storm on the night of the accident as a sudden increase in wind speed caused by a thunderstorm – dangerous, but in principle manageable for experienced seafarers. As key evidence, the investigators point to the neighbouring vessel, the ‘Sir Robert Baden Powell’, which weathered the same storm in the same bay without suffering any significant damage.

The following are to be charged Three crew members: Captain James Cutfield, the chief engineer, and a deckhand who was on watch on the night of the accident. The charges include negligent shipwreck and multiple counts of manslaughter. All those charged are presumed innocent.

The Italian public prosecutor’s interpretation stands in direct contradiction to the MAIB’s findings: If a severe thunderstorm was enough to cause the ‘Bayesian’ to capsize due to its design characteristics – and if the crew could not possibly have known about these characteristics because they were not documented in the stability manual – then the question of individual negligence is significantly more difficult to answer.

A legal tug-of-war worth millions

Another player fits into this complex picture: the shipyard that built the “Bayesian”. The Italian Sea Group, which also owns the Perini Navi brand, has filed a lawsuit in a Sicilian court against the holding company Revtom – effectively against Angela Bacares Lynch as its owner – the captain and two other crew members. The claim: 456 million euros in damages. In support of its claim for damages, Italian Sea Group states that it has not sold a single new Perini Navi vessel since the sinking of the “Bayesian”.

The legal dispute is mutual: Angela Bacares has, for her part, filed a claim for damages against the Italian Sea Group. Just one month after the disaster, the company had filed an initial lawsuit against Bacares, but withdrew it shortly afterwards – on the grounds that the lawyers it had instructed had acted without authorisation.

The company’s chief executive, Giovanni Costantino, had publicly described the “Bayesian” as “unsinkable” and stated that the crew must have left hatches or doors open. The MAIB report, however, states that there was no evidence whatsoever of flooding through any openings – according to the investigation, water only entered via the starboard railing when the yacht capsized. The Italian Sea Group also filed a lawsuit against the New York Times, which had reported critically on the yacht’s design.

In the ‘Bayesian’ case, therefore, a criminal investigation, a safety inquiry and mutual civil claims are all taking place simultaneously – with potentially differing outcomes. It remains to be seen which version of events will prevail in court.

Conspiracy theories: plenty of material, no evidence

As if the complex situation weren’t enough, conspiracy theories are also coming into play, fuelling speculation but providing no evidence whatsoever. Mike Lynch was no ordinary private individual. The Briton had played a key role in arranging a meeting that led to the AI cybersecurity firm Darktrace was the result of a collaboration between staff at the British intelligence agency GCHQ and mathematicians at the University of Cambridge. Darktrace employs former agents from MI5, MI6, the CIA and the NSA – and works for NATO intelligence services, amongst others.

Added to this are some striking coincidences: the voyage on the “Bayesian” was intended to celebrate Lynch’s acquittal following a years-long extradition dispute with the US. Among the fatalities were his lawyer and a banker who had appeared as a witness during the trial. Lynch’s co-defendant, Stephen Chamberlain, was struck by a car whilst out jogging shortly before the ‘Bayesian’ sank – and died in hospital a few days later, whilst the world was still learning of the disaster off the coast of Sicily.

Some media outlets have picked up on these circumstances and are reporting on alleged contacts with the secret services shortly before the ship sank, as well as on possible sabotage. The sources remain anonymous and unverifiable. Neither the MAIB nor the Italian public prosecutor’s office has found a single piece of evidence pointing to external interference or sabotage. To date, none of these reports has provided any reliable evidence to help clarify the matter.

Recovery operation completed – investigation ongoing

In June 2025, the ‘Bayesian’ was raised from the seabed in a complex operation costing millions. The 72-metre-long mast – one of the largest aluminium masts in the world – was salvaged separately and taken to Termini Imerese. Since then, international experts have been carrying out a forensic examination of the wreck. The authorities hope this will provide crucial answers: regarding the actual cargo, the position of the keel at the time of the capsizing, and possible points of flooding.

The Italian investigation is due to be completed by the second anniversary of the disaster in August 2026. There is as yet no public timetable for the final MAIB report.

Could the two studies reach different conclusions?

Yes – and that does not necessarily mean that either of them is wrong. The MAIB assesses design flaws, environmental conditions and human factors as a whole, with the aim of preventing future accidents. The public prosecutor’s office must prove whether specific individuals acted negligently or unlawfully. These are related, but not identical, questions.

The MAIB interim report found that the “Bayesian” had a vulnerability under a specific operating condition which was not documented in the stability information manual. Whether and to what extent this will have criminal or civil law consequences – and for whom – is the subject of ongoing proceedings, the outcome of which cannot be predicted at this stage. The investigation into the salvaged wreck is likely to provide both sets of proceedings with important new findings. Until then, the following applies: all parties involved – the crew, the shipyard and the owner – are presumed innocent until proven otherwise by a final and binding court ruling.