The start of March has brought the usual bi-annual number plate change, even if the situation at car dealers around the country is a little unusual. While some motorists clamour to get the first ‘21’ registration numbers others are more interested in the older and more unusual end of the number plate market. Opting for an older plate opens up the door to all sorts of letter and number combinations and allows for personalisation - from your initials to a nickname or something related to our specific car. The Driver and Vehicle Licensing Agency (DVLA) holds regular auctions of registration numbers and there are plenty of brokers who also buy and sell private plates, with prices starting from less than £100. However, they can go for an awful lot more than than, as recent research from Auto Trader has found. The price of the most desirable plates has soared in recent years, reaching more than half a million pounds in some cases. Other plates may be hidden away or haven’t changed hands in years but here are the 21 most expensive number plates sold in the UK in recent years.