smutty british expression?

[Sue Spence]

On 13 Feb 2014 09:55, "Dominic Thoreau" <dominic at thoreau-online.net> wrote:
>
> On 13 February 2014 08:26, Kieren Diment <diment at gmail.com> wrote:
>
> >
> >
> > On 13/02/2014, at 7:00 PM, Sue Spence wrote:
> >
> > > I wish I could get fish for 4p now.
> >
> >
> > "Six pints of bitter," said Ford Prefect.  [...]
>
> > Ford slapped a five-pound note on the bar. He said, "Keep the change."
> >
> > "What, from a fiver? Thank you sir."
>
>
> You'll generally get change from a fiver for *a* pint, but not two. ...

Today I learned that a pint cost about 20p when HHGTTG was written.