A rather posh lady is showing her small daughter around Rome in the back of a taxi. They pass a railway station and the daughter asks: "Mummy, what are all those ladies doing standing around in very short dresses?".

The mother realizes that she is referring to the prostitute day shift, but hedges - "I expect they are waiting for their friends, or looking at the Roman architecture, dear".

The taxi driver flips back the partition and says:

"Go on, a-mother. Tell her they're prostitutes!".

"Mummy what are 'prostitutes'?"

With a sigh, Mother tells all.

The little girl is very interested:

"But Mummy, don't they sometimes have babies?".

"Well yes dear, I'm afraid they do."

"But Mummy, what happens to the babies?".

"Well dear, that's the interesting thing about it: invariably they become taxi-drivers".