BBC1 drama The Replacement has ended, with one or two questions still hanging and the future of the characters unclear – and it looks like it will stay that way.

Because any viewers who are hoping to see more of Vicky McClure, Morven Christie et al will be disappointed: writer and director Joe Ahearne has made it clear that his psychological thriller is definitely not coming back.

“It's very much a self-contained drama,” he said. “I am very much a fan of beginning, middle and end, and quite a lot of drama on telly both here and in America they want it to be all middle. They like it to go on forever.

“When I am a viewer I don’t necessarily want to commit 20 hours of myself to something. So very few stories really repay that. It’s the commercial imperative of TV, it’s what everyone wants," he added.

However, Ahearne explained that the experience of writing for a series for years is "exhausting".

“A lot of writers want something to write for five years. You try writing it. It’s absolutely exhausting trying to find out new angles on a character. How many stories really do you want to be with the same characters for years and years and years?"

Warning! Spoilers follow if you have not seen the concluding third episode of The Replacement

Describing the story of The Replacement as “complete” he added, “I think it’s quite good to leave people wanting more. And also, I think it would be quite difficult to get those two characters together without either amnesia or plastic surgery.”

In an ending which Ahearne described as "bittersweet", Vicky McClure’s Paula was finally captured by police after a dramatic conclusion in which she abducted Ellen and Ian’s baby daughter Leah.

Paula was arrested, but a closing scene showed Ellen by the grave of their friend and colleague Kay – who was murdered by Paul in episode one – with daughter Leah. 

In the very final scene Ellen is reading Leah – who is now a toddler – books about architecture before Kay's widow David (Dougray Scott) hoves into view and is about to join them.

While Ahearne will not be revisiting this story, his work will be seen again soon when his next film project – a "gay thriller" called B&B and starring former Doctor Who star Paul McGann – is released later this year.

The film is about a gay couple played by John Bateman and Sean Teale who visit a bed and breakfast run by a devout Christian. The couple “get into trouble” when they start winding up the owner and a sinister visitor arrives, Ahearne explained.

Catch up on The Replacement via BBC iPlayer