Southampton Itchen MP John Denham says Mrs Thatcher's changes had an adverse effect on many people.
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Southampton's marathon runners worked up a sweat as temperatures touched 20c but there was help on hand to keep them cool.
The Duchess of Cambridge has been driven to St Mary's Hospital in London in the "early stages of labour", Kensington Palace has said.
The Duchess of Cambridge has been on maternity leave since the week before Easter.