Lloyd's underwriters will be among those celebrating the first £1m winner of Who Wants to be a Millionaire this week – they stopped insuring the prizes on the show in August after a dispute over how questions were chosen.

And their reason could support the BBC's allegations that ITV bosses may have dumbed down the questions in order to win the ratings war with One Foot In The Grave.

Insurance Times understands that in January the syndicates announced a review based on claims the show was not allowing the questions to be audited thoroughly. In August this year, some syndicates decided to pull out.

One Lloyd's underwriter said: "Basically, the insurance pays out if the total prize pay-outs exceed the prize fund.

"But the prize fund was getting lower and several underwriters queried if Celador [the production company] were allowing the auditors to audit the questions properly."

The fund for the show comprises the money received from callers eager to participate as well as surplus revenues from previous series.

After the initial series, the prize fund surplus stood at just under £500,000, and then increased to more than £1m, meaning insurers never had to pay. But the syndicates grew nervous when the prize fund started to dwindle.

The show's new lead underwriter is American giant AIG but the underwriting structure has changed. If contestants win more than £2m in the series, then AIG pays. However, the only winners that count are those that win either £500,000 or £1m.

Celador was not available for comment.