This play is a masterpiece immaculately performed. I started from the beginning writing down the witty lines, until I realised, I had filled half a notebook. My pen never left the page.

Gore Vidal wrote The Best Man in 1960. The Americans are holding an election. The Democrats have gathered to choose their candidate. It’s not the best man who will win, it’s the one who’s most convincing.

This is dirty tricks city. Two politicians work to tear each other apart.

The skill is to turn the public against the other one while not actually upsetting the voters. At one point someone says: “We are all interchangably inoffensive.”

One of them will get the backing of the outgoing president – each thinks the other man will be chosen.

Vidal wanted to be remembered as “the person who wrote the best sentences of his time” and these lines are not just theatrical gold, they are still pertinent.

Little has changed. The fight between Democrats Hilary Clinton and Bernie Sanders allowed Republican Trump to win the election.

The audience enjoyed all the inferences. They roared and applauded at the line: It’s not his being a bastard, it’s his being a stupid bastard.”

The play has a refreshingly classy cast. This is theatre at its absolute best. Martin Shaw and American film actor Jeff Fahey play the candidates. Shaw is the “decent” character, Secretary William Russell. Fahey plays the cynical one, Senator Joseph Cantwell. Russell has a middle class wife, Alice, played by Glynis Barber dressed stylishly in little suits and navy dresses.

Mrs Mabel Cantwell, played by Honeysuckle Weeks, is a girl from the deep south in her bright yellow dress and little white cardigan The body language of both is a joy. As they give a joint interview for the press, Weeks poses for the camera like a calendar girl. Alice is more considered. When challenged about her influence, saying: “I’d like to think that politics is contagious but I am afraid it isn’t.”

The play is set in a plush hotel where the candidates have arrived for the Democratic convention. We see a suite of sitting room at the front of the stage and bedroom behind it. To switch between the rooms from earnest Russell to unscrupulous Cantwell only the colours of the cushions and the bedspread are changed - from duck egg blue to cerise. Strange how it works.

There are laughs all the way through but Jack Shepherd as former President Hockstader has some of the best lines delivered with impeccable comic timing. He tells Russell that people don’t mind voting for a rich person these days. “If you have a lot of money of your own, they think you won’t go stealing theirs.”

As for religion, in his day he says: “You had to pour God over everything, like ketch-up.”

On Russell being a serially unfaithful husband, he remarks: “Immoral? Presidents don’t come in any other size.”

The cameo parts are brilliant. Gemma Jones, sweeps in regally as the grand dame of politics advising the wives: “Don’t take too much interest like Mrs Roosevelt and don’t take too little like Mrs Eisenhower.”

David Tarkenter is wonderful as the nervously servile informer, Sheldon Marcus who arrives to offer Secretary Russell and President Hockstader the dirt on Senator Cantwell from their army days.

As I left the theatre, I realised that apart from “bastard” there is no swearing. Whereas so many American films just have grunts between the expletives rather than dialogue, Vidal glories in rapier sharp wit. They are the best sentences of our time too.

The Best Man is at Cambridge Arts Theatre until Saturday, October 21.

Angela Singer