Top Kent businessman Darrell Healey is facing a £6 million bill after a £30 million “superyacht” deal went sour.

Mr Healey, chairman of Ashford-based construction firm the Groundworks South East (GSE) Group and principal of the GSE Racing superbike team, underwrote the yacht deal with his personal guarantee and must now pay the price after a High Court judge’s ruling on September 3.

Speaking after the case, he said: “We’re appealing against the decision and it’s going to the court of appeal.”

Mr Justice Blair said the contract for construction of a 60-metre “superyacht” - at a price of 38 million euros - was signed between an Isle of Man company, wholly owned by Mr Healey, and elite Italian boat builders, Azimut-Benetti SpA, in September 2008.

The delivery date for the yacht was in November 2011 but the contract included a clause that 20 per cent of the total purchase price would be payable if the deal fell through.

The judge said there was no dispute that the first instalment of 10 per cent of the purchase price, due in October 2008, was not paid. The yacht builders, 15 months later, terminated the contract and demanded their 20 per cent - a total of 7.6 million euros.

At the High Court, Mr Healey’s lawyers argued that figure far and away exceeded the yacht builders’ true losses and should be viewed as punitive and unenforceable.

However, upholding the validity of the 20 per cent clause, Mr Justice Blair said it was “commercially justifiable as providing a balance between the parties”.

He told the hearing: “This was a contract for the construction and sale of a very expensive yacht, aptly described in the evidence as a 'superyacht’.

“Both parties had the benefit of expert representation in the conclusion of the contract. The terms... were freely entered into. In a commercial contract of this kind, what the parties have agreed should normally be upheld.

“The clause in question is not even arguably a penalty, and is enforceable in its terms.”

The judge’s ruling means that, in line with the personal guarantee he gave in September 2008, Mr Healey is now liable to pay the yacht builders 7.1 million euros, as well as forfeiting a 500,000 euros deposit.