WHAT did a 20-year-old David Edgar make of events in 1968?

I was very inspired by them. I came to university from a public school, where I’d been involved in CND and was very much opposed to the Vietnam war.

But when I got there, I was quite taken aback by the revolutionary left, whose rhetoric and politics were much further to the left than anything I’d come across before.

In April 1968, I found a mentor — a leading radical student — who said to me just after the Tet offensive: “Why do you think the Viet Cong were able to get into the compound of the [US] embassy?

“This peasant army against the greatest military force the world had ever seen — it’s because they have the support of the Vietnamese masses.”

That was a massive eye-opener. Then I connected that with the Black Panthers and the two black athletes who raised their fists at the Mexico Olympics and the events in Paris in May of that year.

All these events taking place across the world seemed to confirm this idea of the masses being enabled by history to rise up and make a better world. Like millions of people around the world, I was inspired by the events I saw all around me.

Were you rebelling against your family?

I was rebelling, but I think it was much more positive than that. I think it was what was happening in the world. You would have had to be very set in your ways to be at university in 1968 and not be inspired by what was going on in the radical movements globally.

You describe the show as a conversation between yourself now and 50 years ago. Is it an autobiography?

Although I wrote every word and it’s my show and my story, I worked on it in a way that is much more akin to the way devised theatre is made.

There was a great deal of decision-making needed in order to tell a coherent story that didn’t claim to be a full autobiography. It was very much dabbing onto particular incidents.

Has the show changed during the tour?

We’ve changed some things for artistic reasons. I felt that politically we were in danger of it becoming too specific — we talk quite a lot about the 2017 election — so we’ve made the contemporary a bit more general.

The other big thing that has happened politically is Extinction Rebellion. That’s now in the play and it wasn’t last year because it didn’t exist. To that extent, we are responding to events, but it’s difficult because if we were responding to day-to-day events we’d have to be changing the show every night at the moment.

We actually close this run on October 31 — Halloween — and supposedly Brexit night. One of the main questions the play asks is why the Sergeant Pepper generation voted for Brexit? Why was it that 60-year-olds were much more likely than 20-year-olds to have voted Brexit?

That question is very vivid and lively. That may or may not remain so after we do or possibly don’t leave.

Has performing the show shifted your perspective at all on acting?

Yes. One of the things a writer tends to do sitting up in the stalls, particularly when a play is up and running, is to gently say to the director: “I wish the actor would deliver this line in the wonderful way they did it yesterday.”

But, actually, you realise that if you have an idea to keep something fresh, that might have an impact for two or three pages.

When you are in the moment, things can go in different directions in a very creative way. I’ve got much more interest in the things that actors change in a performance, as well as being much more sympathetic to the various difficulties and dangers that actors have on stage.

Where might we be in another 50 years’ time?

The play asks that question, but about 30 years on, when I would be 101 years old and what the world would be like then.

There is much speculation about whether humans will still be eating meat, would single-use plastics still exist and would people still be flying. We ask those questions to challenge the audience.

The play is quite optimistic about the achievements made in the social and cultural spheres, gay rights being an obvious example but also great gains in terms of civil liberties and the role of women in society.

Less spectacularly so — and there is a long way to go in terms of ethnic equality — it is still better to be BAME in Britain now than it was in the early 1970s. There has been a lot of gains, but there have also been spectacular things that haven’t been achieved.

I read through various political manifestos, including the Communist Manifesto, just to see things that should have been achieved but haven’t been.

There is a long way to go and I hope that we don’t have to wait 50 years to see slavery abolished throughout the world, various civil liberties that are by no means universal and the right to join trade unions — something that is in the Universal Declaration of Human Rights from 1948 but still has not been universally achieved.

Trying It On tours until October 31, visiting Gulbenkian Studio University of Kent, Warwick Arts Centre, Clapham Omnibus Theatre London, Tobacco Factory Bristol, Northcott Theatre Exeter, York University Theatre, Derby Theatre and University of East Anglia Studio, details: chinaplatetheatre.com