Tuppence Middleton on OCD and playing Elizabeth Taylor

Actress Tuppence Middleton says she has "woken up bolt upright in the middle of the night" since rehearsals began for her latest play.

The 36-year-old actress, who has obsessive-compulsive disorder (OCD), says "anxiety" is to blame.

Middleton's new play sees her portray the Hollywood star Elizabeth Taylor in The Motive and the Cue, opposite Johnny Flynn as her husband Richard Burton.

The actress's OCD means one of her worries is kissing her co-star.

"Johnny and I have to kiss in this [play] and one of my obsessions is being emetophobic, that's fear of vomiting," Middleton tells BBC News.

"And so I get preoccupied with, 'oh what if Johnny has norovirus'?"

Middleton developed OCD as a child and told the BBC about the hidden and "internal" impact it has on her career.

The beginning of rehearsals for The Motive and the Cue was particularly challenging.

"The first day when you meet everyone, and everyone shakes hands and I'm making a mental note of whose hand I've shaken and then I have to remember while I'm talking to people that I need to go and wash my hands," she explains.

As well as an intense fear of vomiting and a preoccupation with cleanliness and contamination, Middleton told One to One on BBC Sounds in 2021 that her OCD also manifests itself in obsessive mental counting and compulsive checking behaviours.

But now, she says: "You find ways of coping with it as you get older and get used to it."

Obsessive compulsive disorder affects more than 500,000 people in the UK. Sufferers can experience anxious, intrusive thoughts and, like many medical conditions, OCD can get worse if left untreated.

OCD can be difficult to spot as sufferers may hide their symptoms because of feelings and thoughts of guilt or shame or embarrassment.

There are some common thoughts or behaviours the sufferer may experience, and may often know are irrational. These can include:

Middleton has succeeded in building a wide-ranging CV of film and TV work, most notably in science fiction, including Black Mirror and Sense8, and costume dramas such as the Downton Abbey movies and War & Peace. She was seen recently in the ITV thriller Our House.

But The Motive and the Cue is her first major stage role. She admits it's "very daunting" playing Elizabeth Taylor, an actress as famous for her personal dramas as her professional career, who was married eight times and lived a tumultuous life in the spotlight full of scandal, alcohol and addiction.

In the Motive and the Cue, directed by Sam Mendes and written by Jack Thorne, who also wrote Harry Potter and the Cursed Child, Taylor is newly married to Burton.

The couple had met on the set of the film Cleopatra and embarked on a passionate affair, while married to other people.

They created a sensation wherever they went and became in many ways the first "celebrity couple", long before Brangelina, Bennifer or Kimye.

Middleton says it's hard for younger people to understand now, nearly 60 years later, "just how famous they were".

"They were sort of like exotic animals," she says, "people wanted to be close to them."

The play is set in 1964 when both were at the height of their fame and Burton played Hamlet in an experimental production on Broadway directed by John Gielgud.

"Every single night, throughout the run," explains Middleton, "there were thousands of people in the street outside the theatre and the roads were blocked off.

"And that would just never happen now, because celebrity doesn't hold that same kind of pull."

The Motive and the Cue is at the National Theatre: Lyttelton from 20 April to 15 July.