Conversation so far:
Where did Tony Benn retire from?
He retired from the Parliament and the Cabinet.
When did Tony Benn retire?
He retired from the Parliament in 2001.
what is a signatory?
The writer of a signature is a signatory or signer.
is there anything i should know in the article about Tony Benn?
Benn was a signatory to a letter, that was published in The Guardian newspaper condemning raids of more than 50 brothels in the central London area of Soho.

Question: why were they arrested?
Self-contained rewrite: Why were the women from the brothels arrested after Tony Benn was a signatory to the letter published to the guardian newspaper?