Actor Martin Freeman, who played Dr Watson on Sherlock, has hinted that the beloved series may not return anytime soon as making it is "no longer" fun for the cast.

Benedict Cumberbatch played the eccentric detective in BBC's modern interpretation of Arthur Conon Doyle's work.

The series became a massive hit as soon as it aired, making Cumberbatch an international star while cementing Freeman's reputation as one of the finest British actors, but managing fans' expectations has not been easy for the producers.

"Not massively. Um I think after series four (it) felt like a pause. I think we felt we'd done it for a bit now. And part of it, speaking for myself is (due to) the reception of it," Freeman told The Telegraph when asked if there were any talks about a fifth season.

The fourth season of the show, which aired last year, could not match up to its previous outings but Freeman believes it is impossible to deliver on that.

"To be absolutely honest, it (was) kind of impossible. Sherlock became the animal that it became immediately. Whereas even with (the UK version of) The Office, it was a slow burn. But Sherlock was frankly notably high quality from the outset. And when you start (that high) it's pretty hard to maintain that. Being in that show, it is a mini-Beatles thing. People's expectations, some of it's not fun anymore. It's not a thing to be enjoyed...", Freeman said.

Sherlock premiered in 2010 and became an instant sensation in the UK and then in US before finding a global audience.

Freeman recently featured in Marvel's Black Panther while Cumberbatch already has his own superhero persona of Doctor Strange in the studio.