The two children of an unknown Sussex punter will each receive a cheque for £10,000 if their father survives until his 100th birthday on July 8.

William Hill bookmakers revealed the unusual bet as it slashed odds on Britons living to 100 amid fears of payouts totalling millions of pounds, it emerged yesterday.

The firm has paid out nearly £20,000 on centenarian bets in the last few months.

Hill's spokesman Rupert Adams said: "Since these payouts we have been looking in to the potential liabilities for our centenarian bets and so far we have identified potential liabilities of £35,000 in 2005 alone.

"They include a punter from Sussex whose two children will receive cheques for £10,000 each if their father makes it to 100 on July 8."

He said: "There are also bets of £10,000 and £5,000, both of which become payable in June.

"When we first started offering these bets, people very rarely made it to 100 but it seems to be coming more of an everyday occurrence and I cannot see us being anything like as generous with our odds in the future."

On January 2, Arthur Best, from Welshpool, south Wales, won £7,370 on his 100th birthday while in November last year, Jennifer Strover of Sudbury, Suffolk, collected more than £12,000 after she placed a bet that her mother-in-law Rosalind would make it to 100.