A rare £5 note fetched £2,800 on eBay, and this is the small detail you should be paying attention to in order to find out if you could be sitting on a fortune.

The serial number on the note is the key.

(Image: Gareth Fuller/PA Wire)

These are the prefixes to look out for on each bank note which is an indicator as to whether or not they are valuable:

£10 notes – HB 01

£5 notes – CA 01

£20 note – EH 01 prefix (followed by a low number like 000002 or 000003)

The £5 note sold on eBay had the serial number CA01 000046, making it extremely desirable for collectors.

Recommend Reading

Five incredibly rare and valuable British coins

Rarest 50p coins in circulation the UK?

The Royal Mint has revealed the most valuable 50p coins in its collection.

The rarest is the Kew’s Garden 50p, which was designed to mark the 250th anniversary of the gardens in 2009. Only 210,000 coins were ever minted with this design.

The Kew Gardens 50p sells for £156.25 on average, but one seller received over £700 for one when they sold it on eBay.

The other rarest coins stem predominantly from the 2011 Olympics, with the wrestling, football and judo coins among the most valuable. Only 1.1million of each of these coins were produced.

Flopsy bunny and Peter Rabbit designs which were produced in 2018 are also highly valuable.

These coins – 1.4 million of which were minted – depict the characters from Beatrix Potter’s novels and celebrate the life of the English writer and these sell for around £5.

In 2019, 500 million coins were produced, with three new 50p designs.

These included one of Arthur Conan Doyle’s Sherlock Holmes, Paddington Bear at St Paul’s Cathedral and the Tower of London.

Top 10 most valuable 50p coins, according to Royal Mint

Here is a list of the top 10 most valuable coins, when they were made and how many were minted:

Kew Gardens (2009), 210,000

Olympic Wrestling (2011), 1,129,500

Olympic Football (2011), 1,161,500

Olympic Judo (2011), 1,161,500

Olympic Triathlon (2011), 1,163,500

Peter Rabbit (2018), 1,400,000

Flopsy Bunny (2018), 1,400,000

Olympic Tennis (2011), 1,454,000

Olympic Goalball (2011), 1,615,500

Olympic Shooting (2011), 1,656,500