J. Smith-Cameron underwent emergency surgery earlier this month

She told The Observer magazine: "I don't know whether you're aware of this, but I had to have an emergency appendectomy.

"And I'm still sort of getting my strength back

"It was a big thing, and my husband couldn't come because he's opening a play in New York."

The actress had called the theatre to explain she couldn't work because a pain in her abdomen meant she could "barely straighten up", and a doctor was called for her, and she was advised to go to hospital as soon as possible.

She said: "They admitted me straight away, and put me on antibiotics. There were more urgent surgeries than mine, so then I had to wait a day.

"I came out on a Friday evening, and they [the company] didn't call me; they let me rest until the following Tuesday, and then I did half-days for a while, which was draining, but also good. This was, I guess, two weeks ago.

"Today is only my second full day back. Everyone has been extremely gracious and understanding and... I know, I know! I'd been looking forward to all this for weeks. I was so excited, and then all hell broke loose."

Despite her ill health, the 67-year-old star - who has daughter Nellie with husband Kenneth Lonergan - feels "lucky" because she received such "wonderful" care at St. Mary's hospital in the city.

She added: "But I just feel very lucky. I want to do a whole series about St Mary's.

"They were wonderful. They were rock stars. I sent over a gift for them today because - oh my God - they were so skilful and hardworking, and their work ethic was so aggressive, you know?"

Previews for the play - which also stars Mark Rylance - begin in three weeks and Smith-Cameron believes she will be ready for opening night.

She said: "Touch wood. Everything is fine, apart from me being a little behind."