Alan Bennett is surprised. Surprised that the audience found his latest play funny. “I had no notion,” he says, “I thought they would be shocked”. I am one of a scribble of journalists taking tea and biscuits in a National Theatre meeting room with the playwright, screenwriter, actor and author. We have just emerged from a sparkling midweek matinee showing of his new comedy, and yes, People had the audience in stitches, but it is quite a provocative piece in which Bennett has a dig at institutions such as the Church of England and the National Trust.

Great British Life: Sin Philips as Dorothy and Brigit Forsyth as Iris in PeopleSin Philips as Dorothy and Brigit Forsyth as Iris in People (Image: Archant)

Bennett – the original hipster in a tweed jacket, shirt, jumper and tie - says that he can’t settle in his own mind why he wrote the play, but that it started with a sense of unease when going round a National Trust house and being required to buy into the role of reverential visitor.

Some plays start with an itch he says, but in the case of People it was an image of a woman in a shabby fur coat with gym shoes: “I saw that and then began thinking what is she doing here and where does she belong?”

The woman wearing fur coat and gym shoes is former model Lady Dorothy Stacpole (played by Siân Phillips) who lives in a crumbling and perishingly cold mansion in Yorkshire with her companion Iris (Brigit Forsyth). The play hinges on the future of the house – June, Dorothy’s archdeacon sister (Selena Cadell) wants to give it to the National Trust, while Dorothy would rather it be used as a location for a porn film.

The play has ruffled some National Trust feathers. When it first came out Simon Jenkins, Director of the National Trust condemned it in an article he wrote for The Guardian. “I think he rather regretted that,” says Bennett. “Someone who was sitting behind him in the performance said he was in fits of laughter all the time.

“What slightly galled me momentarily was that it was assumed that the main character is the voice of the author, and so I endorse everything that Dorothy says. Some things I endorse, but not all. You can’t pin down the message of a play by what the main character thinks. It’s a tour around.”

The Church of England also comes in for a bit of stick, but Bennett says he feels nothing but benevolence towards the institution: “When I was young I thought I would end up in the Church. There’s nothing I like better than going round old churches, though my partner Rupert, who is more aesthetic than me, only likes churches that show no sign of religion.”

People is directed by Nicholas Hytner who Bennett has successfully collaborated with on previous hit productions including The History Boys, The Lady in the Van and The Habit of Art. He describes their relationship as “a funny one”.

He muses: “It ought to be a master and pupil in terms of our age, but it’s the other way about. I feel I want to please him, or to please the Theatre and that’s my great spur.”

Bennett clearly enjoys the process of working with Hytner: “I’m involved with the casting process. I come to rehearsals every day. I like it - it’s so gregarious. Nick has made the National Theatre a comfortable place. I rewrite a lot. I have only learnt to rewrite through the process of rehearsal.”

Does he find the act of writing gets any easier? “I have to say it doesn’t. I enjoy dialogue, but always find plots difficult, and getting characters on and off stage. When I was younger I would drink to make it easier - maybe a small bottle of whisky, enough to get me tipsy. But I realised that wasn’t a good idea.

“I haven’t got a computer. We had one once but it was stolen and we haven’t bothered replacing it. I write with a pen. I like jelly pens, they are very free-flowing. I used to transfer my writing to the typewriter, but they are harder to find and to get mended when they break down. Plus I get arthritic hands, so they have to transcribe my writing here at the theatre from bits of paper stuck together.”

In the play Dorothy says “people spoil things”. Does Bennett agree? “Where I live in Primrose Hill, weekends are totally spoiled by people. And I used to visit a wonderful church in York, the Holy Trinity in Goodramgate, which is now regrettably thronged with people. But I can’t say people shouldn’t go, other people have just as much right to go there as I do.

“I actually heard a child say that people spoil things. I thought ‘he’s saying something nobody else would say’, though I agree with him. Other people do spoil things, but I don’t.”

How does Bennett feel about turning 80 next year? “I get no consideration for my age, because most people think I am younger than I am,” he says. “It’s because I have kept all my hair and it hasn’t gone grey. It must be the genes, my brother is the same.”

So how will he mark his 80th birthday? “I won’t do anything really. I hope nobody will notice. I can still ride my bike. I find it easier than walking. When I came for the first day of rehearsals a staff member at the entrance remarked: ‘Oh hello, still hanging on then?’ It did slightly take me aback.”

Bennett has said he thinks he is “over-appreciated but underestimated”. He elaborates a little: “People like what I do but I don’t think they know what I have done. When I am gone and they go through my work, they may see a harsher side and maybe a more thoughtful side than is given credit for now.” n

• People – a National Theatre Touring production - comes to The Lyric, Plymouth Theatre Royal, from 12-16 November. Box Office: 01752 267222.