A Lloyd's name has been ordered to pay £15,000 to underwriters, despite the syndicate being unable to prove any written contract ever existed.
Margaret Woolley refused to pay two cash calls to the company managing the affairs of P&B (Run-Off) in October and November 1996, claiming she had no relationship with them.
She argued that as syndicate 103 could provide no documentary evidence of its relationship with her managing agent, she did not need to provide funds to back its underwriting.
But a recent high court ruling threw out her claim, saying that although no agreement could be found, it had existed but had subsequently been lost.
And Mr Justice Andrew Smith added that even if the signed contract had never existed, the way the parties behaved at the time suggested a valid and enforceable, if only verbal, contract was in place.
Woolley, of Stratford-upon-Avon, has now been ordered to meet the demand for extra money.
Speaking after the ruling, Lloyd's welcomed the court's decision.
Sean McGovern, who heads up Lloyd's legal team, said: “We welcome the clear and decisive judgment in this matter which upholds Lloyd's chain of security.”