Bircham Dyson Bell has defeated a professional negligence claim, but with embarrassment all round as the judge described the partner's "sloppy" work and holding that the claimants were massive liars.

Real estate partner Michael Parker didn't spot that a guarantee given to a lender by his client, property developer Harding Homes, contained an onerous 'all monies' clause. When the lender demanded repayment of the entire loan under the clause, Harding Homes sued BDB for professional negligence. In the end the clause was not called upon, but BDB's client argued in the High Court that its existence gave the lender leverage in negotiations over the debt.

"Details? That's why I have associates!"

But Mrs Justice Proudman found for BDB, which had accepted that it committed a breach of duty, and awarded Harding Homes only nominal damages. In a stinging judgment, she said that the owners of Harding Homes, one of whom was a former estate agent, regarded "lies as part of regular negotiation practice". Untruths were such a regular part of their lives, she said, that she "was not able to tell whether and when they were telling me the truth".

But Proudman was also unimpressed with Parker's evidence. She said that she suspected that he regarded himself as "a man of commerce rather than a typical solicitor", and gave a humiliating critique of his working style. He "plainly cut corners all the time in his practice", she said, describing how he did not send out formal engagement letters, didn't provide bibles of executed documents, did not take full meeting notes, was "sloppy" dating documents and saw "nothing wrong" in getting witnesses to sign documents subject to amendment. "It is obvious that such practice constitutes an accident waiting to happen," said Proudman, "and the accident did in fact happen in this case".

BDB did not respond to requests for comment.