He defeated Daleks and Cybermen, but Doctor Who had a problem watching his own son on stage – and it would wipe him out faster than any alien.

David Troughton has revealed how his father Patrick – the second-ever Dr Who – had to avoid seeing him act in the theatre, or he would be ill.

“That’s why my father never did much theatre,” explained Troughton. “He was physically sick before a performance – he took it really seriously.”

With a tender note of sadness, he added: “And that’s why he never came to see me in anything I did and I only learned later – he wrote a little letter, saying the reason was ‘I’d be too nervous’. He would get too nervous for me, too nervous watching me, so God knows what it was like when he was going on stage.”

Veteran performer David, 66, has had no such qualms as his extensive range of acting roles on stage, screen and radio attests.

This most versatile of actors is currently playing Gloucester in the Royal Shakespeare Company production of King Lear, with Sir Antony Sher in the title role, now transferred to the Barbican, London.

Troughton is also the voice of Tony Archer in the much-loved, long-running, radio series The Archers and played villain Ricky Hansen in hit TV series New Tricks (“I really enjoyed that, they’re such a lovely bunch of reprobates”).

And, as we shall see later, he’s not averse to giving orders to Royalty.

Though softly spoken offstage, Troughton has a commanding presence in the theatre, but is without preference when it comes to roles on screen, stage or radio.

“Er, no, my preference is to work,” he replied, in a resigned tone.

He has also had a long innings in terms of his association with Dr Who, which opened with his father playing the Time Lord during the 1960s.

It continued when he shared digs in the 70s with and acted alongside another Dr Who, Colin Baker, who was also the best man at his wedding to Alison Groves.

Yet another Dr Who and good friend, Peter Davison, co-starred with Troughton in hit TV series A Very Peculiar Practice.

And Troughton even took on his father’s role as the second Dr Who for an audio play in which he played opposite the fourth Dr Who, Tom Baker.

But his father Patrick, who features in new Dr Who DVD release The Power of the Daleks, always refused to rely on the widespread TV fame that Dr Who brought – to the extent that he would send “availability” postcards to directors when he was after a new role.

“Dr Who was just a children’s programme then,” said Troughton. “It wasn’t the big thing it is now. My father would have died if he had to do what the new Dr Whos have to do now, come through smoke in front of an audience, ‘This is the new Dr Who’ sort of thing.

“No, he treated it as a character part and that was why he did it for only three years because he was desperate not to be typecast. Nowadays, that would be the opening to anything he wanted to do, but in those days being typecast was terrible. Mustn’t do adverts – no one did adverts – because if you did adverts, that meant you were down on your luck. Now, everyone’s desperate to do an advert and get a hundred grand or whatever it is.

“He used to write every time he knew he was going to be out of work,” added Troughton. “He would write countless numbers of postcards. He would go around the BBC to all the directors’ offices, just knocking on all their doors, saying ‘Anything for me?’. Imagine doing that now! He wrote the postcards pre- and post-Dr Who. He hated being out of work. He had a pathological fear of being out of work.”

But the Troughton dynasty of actors is hardly likely to die out in the near future, as David’s children Sam and William are also in the profession – as is his nephew Harry Melling, who played Dudley Dursley in the Harry Potter movies –and even his grandson looks like following in the family tradition.

But where did it all begin?

“Well, all I know is my great-grandfather and grandfather were great amateur actors,” explained Troughton. “One of them liked singing and one of them liked performing. They were mainly solicitors and my father took it a step further and he was the first professional actor.

“Then the line carried on…bloody hell! My nephew, my wife, my wife’s mother was working with my father in 1948 when she was pregnant with my future wife and I hadn’t even been thought of! And my eldest and youngest are both actors. And I think my grandson will go that way, so it really is quite extraordinary.

“But you only know what you know. If my father had been an accountant, I might have been an accountant. Obviously, I’d got it in my genes.”

On his latest Shakespearean role, Troughton, who now lives in a little village south of Stratford upon Avon, where he and his wife moved after their grown-up children left home, said: “I bring something new to the role of Gloucester because every person interprets it in their own way. I like breaking the mould of people’s appreciation of what Gloucester is like.

But what happens in Lear’s palace affects the whole world – it’s a brilliant play to do, what with Brexit going on – we’re in a situation where you don’t know what’s going to happen.”

The actors he admires most include Karl Malden – “always on screen” – and Anthony Hopkins – “I acted with him once. He was Lloyd George in a BBC series called The Edwardians, he had us in stitches all the time because he was just a brilliant mimic and he had a devil-may-care attitude – reminded me of my father.”

Despite being one of Britain’s greatest classical actors, though, Troughton admitted: “I’d like to give up now, but I can’t afford to. I didn’t know what else to do and you have to earn money. I’ve done it for 40 odd years, so I think I should get a medal for still being here.”

But the thought of eking out a more handsomely rewarded payday in Hollywood is anathema to him.

“Good Lord, no!” he said, his voice rising. “I’d rather stick a needle in my eye!”

And he feels similarly about televised or filmed performances of theatrical productions.

“Theatre is an event on that evening, with that audience, at that time,” he said. “Travelling there and siting down with people, it’s all part of the experience. It loses something otherwise.”

He added: “It’s a funny profession, though, isn’t it? Wanting to dress up and show off in front of people.

“There’s a lot of people that shy away from that. You do put yourself up for it every time…but what are you wanting? For people to say how good you are, that’s all, basically, isn’t it?

“All actors are, basically, about nine in their heads… you have to be. You’ve got to enjoy it, you’ve got to have fun. There’s no point in putting yourself up there if you’re not enjoying it.

“I mean, I don’t read critics now, but you’re being judged all the time.

“The best buzz is comedy when you make them laugh – that’s a real buzz. Making people cry is easier, you can transfer sorrow more easily.”

On a lighter note, he closed by saying: “I made Prince Charles stand up when he came to see Richard II.

“I was playing Bolingbroke and I got all the audience to actually stand up and waited until they did and, as an audience, they had to do it because it was all part of the coronation scene – ‘I am king, you have to stand up’ – and Charles stood up.

Was he hesitant?

“Yes. But he did, like the good soul he is.”

So, Troughton must be one of the very few people ever to order Royalty about. Did he enjoy it?

“It was good, yes… but it was only pretend, really.”

He paused for a moment, then, thoughtfully, added: “It is only pretend, after all.”

King Lear runs at the Barbican in London until December 23.