The 50th anniversary of the Queen's portrait first appearing on banknotes was marked yesterday.

The Bank of England issued a new £1 note on March 17, 1960 which was the first to carry an image of the monarch.

A new exhibition, A Decoration and a Safeguard, looks back on the past 50 years at the bank's museum in central London.

Curator John Keyworth said: "Kings and queens have been depicted on Britain's coinage since Anglo-Saxon times but it was not until 1960 that the monarch first appeared on a Bank of England note.

"There were two main reasons to introduce the royal portrait.

"Firstly, the Bank had been nationalised in 1946, and by portraying the monarch on its notes the institution recognised that it was now publicly owned.

"Secondly, the highly specialised art of the hand-engraved portrait added a formidable anti-forgery feature.

"Taking into account its appearance on postage stamps and coins since 1952 and on Bank of England notes since 1960, the Queen's portrait is probably the most reproduced image in the history of the world."

Five different portraits of the Queen have been used on banknotes since 1960.

These were by Robert Austin (1960), Reynolds Stone (1963), Harry Ecclestone (1970 and 1971) and Roger Withington (1990).

Letters and material relating to the five portraits are on display at the exhibition which also features previously unseen sketches and artwork from the bank's collection including rejected designs and early unissued banknotes.

A Decoration and a Safeguard - The Portrait of the Monarch on Bank of England Notes was at the Bank of England Museum, Bartholomew Lane, just off Threadneedle Street, London from yesterday.