Nicholas Newlife, from Kidlington, Oxfordshire, placed £4,420 on the long-term wagers with William Hill between 2000 and 2005.

When he died in 2009, aged 69, Oxfam were delighted to discover he had left them his entire estate - including the betting slips.

A flutter on Roger Federer winning 14 Grand Slam titles has already won Oxfam £16,750, after the Swiss tennis ace's victory over Robin Söderling at the French Open last year.

Nick also put £1,520 on Federer to win Wimbledon at least seven times before 2020, at 66/1. If Federer takes the title this year, Oxfam will collect an extra £101,840.

And if all the bets turn out to be winners, the charity's windfall would total over £330,000 - enough to provide emergency rations for 46,000 famine victims, or to supply safe drinking water for 350,000 people.

Cathy Ferrier from Oxfam, said: "We're enormously grateful to Mr Newlife for his generous gift, and will be keeping a close eye on Wimbledon this year as a result.

"Every time someone leaves us a gift in their will, whether a few pounds or a few thousands pounds, it helps us make a huge difference to thousands of lives around the world.

Other unusual legacies left to Oxfam include a pair of gold teeth from a dentist; a letter written by Florence Nightingale; some racing greyhounds and shares in the original Woolwich Arsenal Football Club.

Graham Sharpe from William Hill said the bookmaker would be delighted to pay Nick's winnings to charity. He told Sky News: "When Nicholas wrote to me nine years ago to place the bets, they were straightforward but potentially valuable.

"When the first wins came in he was still alive, but the next I heard was he had died and left his slips to charity.

"I think he was a bit of a loner but we'd be very pleased for Oxfam if they won."

Nick's wagers:

£250 on Roger Federer to win at least 14 grand slam titles before 2020 at 66/1

£1,000 on Andy Roddick to win at least 7 grand slam singles titles before 2020 at 33/1

£250 on West Indian cricketer Ramnaresh Sarwan to make more than 9,000 test match runs by end of 2019 at 250/1

£1520 on Federer to win Wimbledon men's singles at least 7 times before 2020 at 66/1

£1,000 on Andy Roddick to win at least 7 grand slam singles titles before 2020 at 33/1

£750 on Andy Roddick to win at least 10 grand slam singles titles before 2020 at 100/1

£350 on Ramnaresh Sarwan to make over 7,000 test match runs by end of 2019 at 50/1

£300 on Ramnaresh Sarwan to make more than 8,000 test match runs by end of 2019 at 100/1

£250 on Ramnaresh Sarwan to make more than 9,000 test match runs by end of 2019 at 250/1