Conversation so far:
when did the old £50 note go out of circulation
By the end of 30 April the old-style £50 banknote featuring the image of Sir John Houblon is being withdrawn from circulation by the Bank of England.
Who is the man in the banknote of the £50  in England
Sir John Houblon was the Bank's first governor. His image was replaced on the new note with Matthew Boulton and James Watt.
Who are the men that replaced John Houblon in England's £50  note
Matthew Boulton and James Watt feature on the new note because they were instrumental in manufacturing coins that were difficult to counterfeit. The note went into circulation in November 2011.
When was the original £50 note first featured in England
The old £50 banknote - was first issued in England in April 1994.

Question: How many are in circulation
Self-contained rewrite: How many £50 note are in circulation in England