A new BBC version of Sherlock Holmes hints at a relationship between the detective and his sidekick Watson.

The series, set in 21st century London and titled Sherlock, is not the first to hint at romance between the pair.

Guy Ritchie’s recent film version, starring Robert Downey Jr, was noted for its homoerotic tension and the actor suggested that Holmes could be a “butch homosexual”.

In the BBC series, which starts this Sunday, Holmes (Benedict Cumberbatch) and Watson (Martin Freeman) cause confusion over the nature of their relationship.

According to reviews, the scenes are supposed to be “comedic”.

In an early scene, when they move in together, their landlady apparently believes they are a couple and says: “There’s another bedroom upstairs … that is if you’ll be needing one.”

The pair also have a meal in London’s gay district Soho, where the restaurant owner says: “Sherlock, you can have anything on the menu for you and your date. I’ll get a candle for the table. It’s more romantic.”

In one scene, Watson asks Holmes whether he has a girlfriend. He replies: “Girlfriend, no. Not really my area.”

Holmes adds: “John, I think you should know I consider myself married to my work and while I am flattered by your interest, I am really not looking for anyone.”

Steven Moffat, who co-created the show, told the Daily Mail: “They are just incredibly good friends. If Sherlock is gay, and who knows if he is, then I don’t think he fancies John.”

Cumberbatch, who plays Holmes, said: “In the books, Watson gets married fairly early on, so I wasn’t aware that it was an issue. However, we do allude to the idea that there may be a ‘misunderstanding’ from other people who think we’re a couple.

“We’ve just moved into a flat-share, we might not be sure what our relationship is at one point, in the same way, when two people meet it takes a while to suss each other out.”

The series is unique in that it places Holmes and Watson in the 21st century, where they grapple with BlackBerrys, laptops and central London’s roadworks.

Instead of Holmes smoking a pipe, he uses nicotine patches and even writes a blog.

The three 90-minute films will be a mix of material from the original stories and new material. The first installment, A Study in Pink, will be shown at 9pm on Sunday on BBC1.