A pregnant policewoman collapsed and died but doctors were able to deliver her twin babies.

PC Sarah Underhill, 37, was rushed to the John Radcliffe Hospital in Oxford from the home she shared with her husband Richard — who is also a police officer — in Wallingford.

The babies have been named James Thomas and Hannah Louise. PC Underhill's father Arnold Whapham tonight said they were both doing well.

James was in intensive care and Hannah was in the hospital's special care baby unit, he added.

Mr Whapham, who is a farmer in North Moreton, near Didcot, said: "She was so outgoing and bubbly. She honestly didn't have a nasty bone in her body.

"She would go out of her way to help people. She was very altruistic. She once received a police commendation for saving the life of someone who had been shot.

"Normally, people keep their distance — peer around the corner to check it's OK — but Sarah wasn't like that. If someone needed help, she wouldn't think twice.

"She couldn't wait to be a mum. She would have made a fantastic mother."

PC Underhill's sister Gill Donkin said: "You couldn't ask for a better sister."

Mr Whapham, comforting his wife Sybil, added: "Sarah never thought of herself first. She was always helping people. Even from her childhood.

"She had a good life. It should have gone on. She should have seen those kids grow up. It's so sad."

Mr Whapham said that his daughter was 35 weeks and five days' pregnant when she was rushed to hospital on Sunday.

He added: "She was with us all at home just the day before. She was just like her normal self. Happy, bubbly, outgoing and so much looking forward to becoming a mum.

"That's how we'll remember Sarah."

Flags at police stations flew at half-mast yesterday as PC Underhill was described as "caring and efficient officer" in the south Buckinghamshire towns and villages she patrolled.

Chief Supt Paul Tinnion, her commander, said: "Sarah will be greatly missed by her family and her many friends and colleagues in Thames Valley.

"Richard is facing a particularly difficult time at the moment.

" Messages can be sent to him through a special police computer mailbox at RichardUnderhillCondolences@thamesvalley.pnn.police.uk.

"I have yet to receive details of the funeral service or the wishes of Sarah's family in terms of attendance."

Her husband joined the Thames Valley force in 2005 and is based in Reading.