A document signed by Oliver Cromwell to help a British merchant captured by pirates is up for sale in Norfolk. 

It sought support for the man who was working on a ship in the American colonies when he was captured and imprisoned in Algeria. 

The letter, which is dated July 7, 1654, was brought in for valuation at The Rostrum Saleroom in Roughton. 

Oliver CromwellOliver Cromwell (Image: Samuel Cooper) Charles Hanson, director of the saleroom, said: “This is such an exciting find. Cromwell is one of Britain’s most important historical figures and the document is a significant piece of seafaring history. 

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“The name on the letter of petition has been confirmed as being consistent with Cromwell's protectoral signature.  

Charles Hanson with the document signed by Oliver CromwellCharles Hanson with the document signed by Oliver Cromwell (Image: Hansons) “In addition, the notation referring the matter to the Admiralty Board appears consistent with Cromwell's hand.” 

The item had been passed down through the client's family for generations and has a guide price of £2,000 to £4,000 when it goes to auction on September 7 at the north Norfolk saleroom.  

The Barbary pirates seized merchant ships in the Mediterranean and North Atlantic throughout the seventeenth century and raided coastal towns and villages across Europe.