Review| The Unfriend at Minerva Theatre, Chichester: 'I gave it a standing ovation'

In many social situations, saying ‘no’ can provoke an almost allergic response – and before we know it we have agreed by omission to something we never would have signed up for in a million years.

It is this phenomenon that former Doctor Who showrunner Steven Moffat taps into so brilliantly in The Unfriend.

A middle-class, middle-aged English couple go on a cruise, and encounter a boisterous American battleaxe who immediately makes it her business to befriend them.

They give her their email address under duress. Mistake number one.

Soon enough, she has wrangled an invite to their house for a week – and a quick Google search of her name reveals she is a suspected murderer.

What unfolds is an increasingly ridiculous and hilarious situation.

To the couple’s horror – expressed with little more than a quivering upper lip or a side glance at each other – Elsa befriends their children.

Before they know it, their lives are being enriched by this femme fatale in a designer tracksuit.

As Elsa, Olivier winner Frances Barber is fabulous: imagine a more happy-go-lucky and less dowdy version of Annie Wilkes, minus the hobbling and with a bit of Mary Poppins (or ‘Murder Poppins’ as she is referred to) thrown in for good measure.

Her raspy drawl and sheer charisma had my eyes and ears glued to her whenever she was onstage. Who doesn’t love a camp villain?

Thankfully then, there were times when the rest of the cast could shine – Reece Shearsmith gives Barber a run for her money as the uptight and neurotic dad Peter.

He got the biggest laughs of the night, particularly in one inspired scene involving a toilet, a police officer and a potentially poisonous sandwich.

Murder not withstanding, there were so many moments you could relate to – the teenage son calling down from his lair for someone to answer the phone; the passive-aggressive neighbour quarrelling about a garden wall – and it was this which had me hooked beyond the final twist.

The Unfriend has BBC Christmas special and West End transfer written all over it.

I gave it a standing ovation – and I promise I was not just being polite.

Until July 9.