Peter and Lynn Burgess had wanted to transform the garden of their £5,000,000 home in Highgate, north London, but thought an initial quote they were given for the work was too high.

They then asked their friend Basia Lejonvarn, 56, for advice and Polish contractors were found to carry out the work at a lower price in 2013.

But within months, the two parties had fallen out and became locked in an acrimonious ’email war’.

The builders were then ordered to stop working and the Burgesses then returned to the original gardener whose quote they had at first rejected.

The couple claimed the work then cost them £265,000 more than it would have done without their friend’s involvement.

In 2017, they sued Ms Lejonvarn, and won a Court of Appeal ruling which stated that she owed them a legal ‘duty of care’, despite only offering advice on the project for free.

But the following year the High Court dismissed the Burgesses claims, instead arguing that their claims against the architect ‘lacked credibility and conviction’.

Now Appeal Court judge Lord Justice Coulson has ordered the couple to pay legal costs at a punishing ‘indemnity’ rate, which would be over £1,000,000 – and could even reach £2,000.000.

The judge said he was making the order because the couple’s claims against their architect friend had been ‘speculative and weak’ and should have been dropped in 2017.

He also lamented the ‘huge costs’ which had been ‘racked up on both sides’.

Ms Lejonvarn had previously protested that she had only offered her advice to the couple in a ‘non-commercial, informal and social context’ about their garden.

At first, it was ruled that she ‘assumed responsibility’ for the project, until the High Court cleared her of negligence.

Ruling on costs, Lord Justice Coulson said: ‘Mr and Mrs Burgess must have known that after the Court of Appeal judgement their claims were speculative and weak and that all that really mattered now was costs.

‘From then on, they found themselves in an absurd position where they were incurring hundreds of thousands of pound on costs, solely in order to try and recover some of those costs from Ms Lejonvarn.

‘They should have called a halt, because their underlying claims were speculative and weak, but they failed to do so.’

He also noted that Ms Lejonvarn had offered to settle the case for £25,000 in March 2015 so that ‘both sides were spared the acrimony stress and expense of litigation’.

The offer was refused by Mr and Mrs Burgess.