The couple parted after it was said to be damaging Dame Tessa's career, but they were later reconciled.
Former leader of the Liberal Democrats Sir Menzies Campbell, who was a member of the Olympic Board which had oversight of London 2012 said Dame Tessa was "universally popular and respected among politicians of all parties".
In recent months, she moved fellow peers in the House of Lords to tears as she discussed her condition and called for patients to have better access to experimental treatment. Tessa was not just the best in politics, she was the best in humanity.
More recently, she has campaigned for additional cancer treatments to be made available through the NHS.
"She died peacefully at the family home near Shipston-on-Stour in Warwickshire last night, shortly after 10pm. Throughout her illness she behaved with quite remarkable courage".
"She had said at the time that In the end, what gives a life meaning is not only how it is lived, but how it draws to a close", she said in the speech.
"She was the most wise of counsellors, the most loyal and supportive of colleagues, and the best of friends", he said.
Mrs May wrote: "The dignity and courage with which Dame Tessa Jowell confronted her illness was humbling and it was inspirational".
It was as Tony Blair's Labour culture secretary in the early noughties that she championed the capital's eventually successful bid to host the games, in the face of Civil Service and Cabinet scepticism.
"Despite going through all of that and wanting to spend precious time with her family... she gave up so much of that time to continue to campaign, to ask for change, because it really matters", she told the BBC.
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Baroness Jowell, an ex-culture secretary who had been diagnosed with a brain tumour in May past year, suffered a haemorrhage two days ago.
John Bercow, Speaker of the House of Commons, described Dame Tessa as an "indefatigable campaigner who translated care from a word to a deed at every turn".
Dame Tessa was employment minister and minister for women, before joining the cabinet as culture secretary in 2001, during which she helped bring the Olympic Games to London. "Our thoughts are with her family".
She was pro-European and in favour of a mixed-economy when both were deeply unfashionable on the left.
This morning party members, journalists and politicians paid tribute to the former MP for Dulwich and West Norwood, remembering her achievements and sharing stories of their memories together.
The world of sport also send their condolences, with Lord Sebastian Coe, the chairman of the London Organising Committee, saying London 2012 simply wouldn't have happened had it not been for Dame Tessa. Without her the sporting landscape of the United Kingdom would have looked very different, and so many other tangible legacies left dormant.
"She showed unflinching tenacity in persuading the prime minister and the cabinet that the government should throw its full weight behind the bid", he said.
"Her determination and sense of humour surrounding them was infectious", he tweeted.
"She just had this capacity to touch everybody she met".