10p

According to Paterson in 1989, the cost of a phone call was 10p. (TV: Survival)

The Fifth Corsair's Ouroboros tattoo was the size of a ten pence piece and located on her upper thigh. (PROSE: Eleven Things You Probably Didn't Know About the Corsair)

Information from invalid sources
A takeaway which Ryan Sinclair once visited sold gravy for 10p. (NOTVALID: The Universe is Calling)