Man of stature behind 'Dear Bill' image
The audience laughed and the newspapers were delighted. But this was not the real Sir Denis. This was the cardboard cut-out from the "Dear Bill" column in Private Eye magazine - a gin-swilling buffoon who preferred golf to the drudgery of Conservative Party politics.
Yet it was Sir Denis’s enterprise and wealth which allowed Margaret Roberts to build her political career. And it was his devotion which saw him play up to the caricature created for him by the media - never overshadowing his wife’s career.
Sir Denis was quick to recognise that by gently promulgating the myth, however inaccurate its foundations, he would be able to escape more forensic investigation. Not for him the personal advisers, stylists and lifestyle gurus who support Cherie Blair in her duties as the current Prime Minister’s wife.
"Better keep your mouth shut and be thought a fool than open it and remove all doubt," he once said.
His strategy was basic but highly successful: "So long as I keep the lowest possible profile and neither write nor say anything, I avoid getting into trouble." Or, as he also put it, his job was to be "ever present, never there".
The other great gift which enabled him to survive the stresses of his role was his exceptional sense of humour. A joke, usually a self-deprecating one, proved the perfect foil when faced with awkward questions about how a very traditional man coped with such a very modern role. Asked who wore the trousers in his relationship, he replied: "I do, and I wash and iron them as well."
Nothing, of course, was further from the truth. As Lady Thatcher revealed in a recent television programme documenting her life, Sir Denis was a small "c" as much as capital "c" conservative.
The son of an industrialist, he was born in Lewisham, south-east London, in 1915, and educated at Mill Hill public school. He served in the army during the Second World War, rising to the rank of major and seeing action in France, Sicily and Italy.
In 1949 he met Margaret Hilda Roberts, then 24, on the night of her adoption as Conservative candidate for Dartford.
She was to become his second wife. The first was a three-year marriage to Margaret Kempson, which ended amicably shortly after he returned from military service. When Alderman Roberts gave Lady Thatcher away at her wedding in 1951, the bride did not wear white. She wore dark blue.
Soon after, Sir Denis’s political ambitions were nipped in the bud when he failed to be elected to Kent County Council. But for the first decades of their marriage, he was the breadwinner - taking his father’s company, Atlas Preservatives, from a family firm to a nationwide business.
He travelled all over to win business, and refereed rugby matches at weekends. His wife was just an aspiring MP, who was not elected until 1959.
It was not until the 1960s that her career eclipsed his when, in 1961, she was made minister for pensions. In 1965, Denis sold Atlas Preservatives for 560,000 - becoming today’s equivalent of a millionaire.
When Lady Thatcher was elevated to the shadow cabinet in 1967, Sir Denis joined the board of Burmah group, which had taken over Castrol. But he decided to shelve his ambitions to support her.
Compensation came in the form of his unrelenting but unobtrusive support for his wife’s political ambitions. Oliver Letwin, the shadow home secretary and a former aide to Lady Thatcher, gave an endearing insight into the value of Sir Denis: "It isn’t easy to be prime minister. There is always part of the day when things seem completely impossible and Denis knew magically how to deal with those. He was the person who exuded something that got one through. Westland; the miners’ strike, he got us through all sorts of things," Mr Letwin said.
Privately, Sir Denis’s views may have been more to the right that those of his wife - he shared Alastair Campbell’s disdain for the BBC, once claiming all BBC people were Trotskyites. But, with one exception, when he bemoaned the disappearance of the pound note, opinions were never shared with the public.
Like the Duke of Edinburgh he was governed by his sense of loyalty; unlike Prince Philip his self-discipline was such that he avoided the gaffes.
Instead, he perfected the ability to follow "the boss" without demeaning himself or overshadowing her. Not that his opinions were not valued, with contemporary witnesses testifying how his opinions were sought on policies, reshuffles and, at the end, the question of resignation.
Lord Carrington, the former foreign secretary, said the public did not realise how much Lady Thatcher relied on him. "Denis Thatcher was a legend in his time. What he deserves to be remembered for, apart from his own career, which was very distinguished, was the fact that he was a wonderful consort to Lady Thatcher. Over the years, he never put a foot wrong," he said.
Sir Denis’s observation of his role was characteristically self-deprecating: "For 40 years I have been married to one of the greatest women the world has ever produced. All I could produce, small as it may be, was love and loyalty."