Have you ever heard of ‘cockney rhyming slang’? This is an East London vernacular which has a particular abundance for terms of money, including ‘Taxi Driver’=£5 (a fiver) and ‘Paul McKenna’=£10 (a tenner). Other cockney rhyming slang terms for £10 include - Speckled Hen = £10, Uncle Ben = £10, Nigel Ben = £10, Ayrton (Senna) = Tenner = £10.