The search is on for 1957 Premium Bond winner

National Savings & Investments is hoping to track down the owners of £40m-worth of unclaimed Premium Bond prizes. The oldest unclaimed prize belongs to a man from South Yorkshire who won £25 in 1957.

Premium Bond prizes are almost unique in that there is not a time limit to claim a prize, unlike the six months' deadline for National Lottery wins. That means it is always worth checking NS&I's website to see if you have an unclaimed prize, even if it is from decades ago.

If you have moved home, for instance, NS&I may not have your new address to contact you about your win. There is no interest on unclaimed prizes so if the South Yorkshire man is found, for instance, he will get only his £25 prize, even though inflation has made £25 in 1957 worth £459.75 today.

But there are plenty of massive wins waiting to be claimed. There is a £100,000 prize won by a London woman in February 2007. There is also a £50,000 prize won by a women in Kent in November 2007. On top of that, there are four £25,000 prizes waiting to be claimed.

There are 740,000 unclaimed prizes, according to NS&I. To find out if one is yours, go to www.nsandi.com/savings-premium-bonds-have-i-won.