I began covering Margaret Thatcher for BBC TV News when she ran for the Tory Party leadership in 1975 and stayed with her to the doorstep of 10 Downing Street in May 1979.

No one expected her to beat Edward Heath. As soon as I saw her steely determination, I had no doubt that Heath was finished. Her campaign was brilliantly organized by former Colditz escaper and Tory fixer Airey Neave.

Mrs Thatcher was presenting cars to disabled people in her Finchley constituency when my news desk told me a bomb had gone off under a car at the Commons and Airey Neave was believed to have been killed.

Film shows me telling her what I’d just learned. Her expression changes but she courteously bids farewell before rushing back to Westminster.

I went on her first trip to the European Parliament. She watched proceedings with evident disdain. She knew nothing about foreign affairs so set out for the Middle East.

Inside the Great Pyramid at Giza, she climbed a steep wooden staircase in high heels. Filming her careful footsteps, I knew this was a woman determined to do things her way.

She declined a camel ride. She knew her predecessor but one Sir Alec Douglas Home had got into trouble wearing an Arab headdress while riding a camel.

In Kuneitra, the Syrian ghost town on the Golan Heights occupied by Israel, she navigated a safe diplomatic path between the warring sides, sitting with the only resident, an elderly woman, chatting over a cup of bitter coffee.

We had the occasional difficult moment but my admiration for her grew.

She was campaigning in the Midlands. She paused in Lichfield to watch a broadcast by Prime Minister James Callaghan. It had been widely predicted he would call the long awaited election.

But, he announced, there would be no election. Mrs. Thatcher was badly shocked.

When she came to be interviewed, she said she would read a statement. I persuaded her to memorise what she had to say. My deadline was looming.

We waited ten minutes while she learned her lines. She then gave a brilliant response. Callaghan’s decision initiated the Winter of Discontent that brought him down.

During the election campaign, she ate a Bakewell tart in Bakewell, picked up a calf in Suffolk and helped push her campaign bus out of the Scottish mud. After her last speech in Bolton, we flew back to London.

Reporters shouted questions. But I asked her to have a drink. She chose whisky and gave all of us a much better interview.

When she arrived in Downing Street as Prime Minister, she gave her conciliatory “Francis of Assisi” homily to my microphone. It didn’t ring true to me and came to haunt her.

After the election, she invited everyone who had been on her campaign to a party at No. 10, with their wives, a thoughtful gesture from someone who was also a wife.

She invited my wife and me to lunch at Chequers. When the WRAF corporal serving the lemon tart dropped a slice on the antique rug, it was Prime Minister Thatcher who ran to fetch the dustpan and got down on her knees to sweep up, assuring the young lady there was no harm done and not to worry.

I was inside the Grand Hotel at Brighton after the IRA bomb exploded. As I filmed Norman Tebbit’s rescue, she displayed her own brand of defiant courage. Margaret Thatcher had survived. And so, she pointed out, had the government. Thus was foiled the most dangerous attack on the British state since the Gunpowder Plot.