Here, in their own words, are the tributes to Sir Denis from the political world.
Conservative Party leader Iain Duncan Smith said: "I am devastated by the sad news of Sir Denis Thatcher's death today.
"Denis Thatcher was one of the most decent, determined and kind people that we have known.
"In a world that so often seems to have lost its manners Denis Thatcher represented so much of what was best in the wartime generation.
'A real zest for life'
"He was always thoughtful and interested in people.
"He possessed a remarkable sense of fun and a real zest for life that bubbled through in every encounter.
"Whether he was enjoying his beloved gin and tonic or playing golf, whether he was meeting people from overseas or visiting people around Britain, he remained true to himself and refreshingly straightforward.
"His role as husband to Lady Thatcher has for too long been unrecognised by commentators and the public.
"He was quite simply a vital element in her success.
"He supported her in all that she did and was incredibly protective of her regardless of the circumstances.
"His common sense and straight talking often helped her in her deliberations and brought him the undying respect of all those who came into contact with him.
"He was also a brave soldier and successful businessman in his own right - a fact often overlooked.
"In all, he was a genuinely rounded individual.
"Denis Thatcher was in his own understated way a remarkable man, a credit to his country, a true and loyal supporter of the Conservative cause and, most of all, a phenomenally strong consort to perhaps the most remarkable Prime Minister Britain has yet seen.
"The Conservative Party and all those associated with it deeply mourn his passing.
"Our heartfelt prayers and thoughts are with Lady Thatcher and her family at this sad time.
"I am proud to have had the privilege of knowing such a wonderful man."
Former Prime Minister John Major
"I think Denis had an impact in a number of ways.
"He was the first husband to a serving prime minister ... He brought a different dimension to the role which was a rather difficult one.
"But I think he did several things. Firstly, he gave Margaret a hinterland, particularly during the difficult days of being prime minister, which otherwise she would not have had. I think that was immensely valuable.
"Secondly, he had very clear and distinct opinions himself and he expressed those opinions, he expressed in private and Margaret more often than not accepted them and took them...
"I don't think Denis set down and said I think you ought to change clause eight of this particular bill.
"But he had a clear set of social mores and a clear set of attitudes and he set those out. And often the prime minister's attitudes and Denis' attitudes were exactly the same, but not invariably...
"His views were robust. Denis was an identifiably English figure. He was in some ways an old fashioned figure, but I don't think that's at all a bad thing.
"He was a figure that was very familiar and very appealing to a large part of what in less delicate times we would have called Middle England."
Former Prime Minister Sir Edward Heath
"The outstanding characteristic of Denis Thatcher was an ability to create good fellowship and enjoy it amongst all those with whom he mixed.
"This included a wide variety of activities, but in particular sporting activities, particularly with a Commonwealth connection with which I was associated as chairman for many years.
"His full-hearted participation was fully appreciated by members of every shade and background. He will be sorely missed and we all extend to Margaret and their children our deepest sympathy."
Prime Minister Tony Blair
"I'm very sad to hear of the death of Denis Thatcher and have sent my deepest sympathy to Lady Thatcher and his family.
"He was a successful businessman, a devoted family man, loyal friend and always entertaining company.
"It was these qualities that enabled him to provide such immensely strong support to Lady Thatcher throughout her long political career.
"He was always by her side when needed, a constant and trusted companion. He will be greatly missed by his family and his many friends in the UK and around the world."
Former Tory chairman Lord Tebbit
"We shall all miss Denis but of course most of all it will be Margaret who misses him.
"He was a quite remarkable man in fulfilling the role which nobody else had filled before."
Asked on BBC News 24 if Sir Denis felt Lady Thatcher should have left No 10 earlier, the peer said: "What went on between them in private, of course, was what went on between them in private.
"I don't think anybody has any doubt that he realised what a strain it was on her and 10 years was an awful long time as Prime Minister.
"We should remember Denis as he was - a great gentleman and a very decent man who put his interests second to that of his wife and his country."
Former Tory leader William Hague
"Denis Thatcher was one of the kindest men I have ever known.
"I will never forget how good he was to Ffion in giving advice about being married to a party leader.
"We will both miss his constant good humour, and always remember the moral and emotional support he gave to a truly great Prime Minister."
Liberal Democrat leader Charles Kennedy
"I was very sorry to hear of the death of Sir Denis Thatcher. He was a stalwart figure on the political scene for many years, and an undoubted support to his wife when she was Prime Minister.
"I would like to send my deepest condolences to Lady Thatcher and the rest of her family at this time."
Former Labour Foreign Secretary and SDP leader Lord Owen
Everybody, whatever their political views, enjoyed the company of Sir Denis: "He liked his gin and tonic and he was good fun."
But Sir Denis exercised great influence: "Most husbands and wives talk about big decisions and he probably influenced her more than anyone else - and not that many people influenced Mrs Thatcher.
"He was certainly not politically correct but his views never landed Mrs Thatcher in embarrassment. It is a selfless, difficult role for a man but he did it well."
Lady Thatcher's former political secretary John Whittingdale - now shadow culture secretary
Baroness Thatcher "would probably not have achieved all that she did had he not been there giving her support.
"Denis Thatcher was held in enormous respect and affection throughout the whole country, no matter what people's political views.
"He made a huge contribution to Margaret Thatcher's political career. He was behind the scenes all the time, giving her support, and I think she and her family will miss him dreadfully.
"Margaret Thatcher wasn't just the first woman Prime Minister, he was also the first Prime Minister's husband, which in many ways was as difficult a job, which he did terribly well.
"He was always there to give her support, but he was always happy to remain two or three paces behind her.
"He was the archetypal Englishman of the old school: immensely courteous, very thoughtful, very generous and immensely supportive of all that Margaret Thatcher achieved.
"Private Eye created this caricature where he was portrayed as being somebody who drank and smoked and went off to play golf.
"It was an awful long way from the real Denis Thatcher, who was an immensely successful businessman and a very sharp operator.
"But he didn't resent the fact that he was portrayed in this way, and occasionally played up to it."
Lady Thatcher's biographer, Daily Telegraph editor Charles Moore
"Denis Thatcher gave his surname to Britain's first woman Prime Minister and his devotion to her and her cause.
"He injected humour and common sense into life at No 10 Downing Street. Everyone who knew him loved him."
Ulster Unionist David Burnside
"We all have our own little memories of Sir Denis.
"I remember a reception in Blackpool about 10 years ago to which Sir Denis came along with his minder and declared: "I don't know what reception I'm at but for God's sake give
me a gin and tonic."