Stephen Fry has told fans he was “very, very happy” to announce his engagement to the comedian Elliott Spencer despite having hoped for a private wedding.

The QI presenter, 57, is said to have begun a romance with Spencer, 27, last year and the pair have been seen together at various public events.

Fry said on Twitter: “Oh. It looks as though a certain cat is out of a certain bag. I’m very very happy of course but had hoped for a private wedding. Fat chance!

“Thank you all SO much for your kind congratulations. Deeply touched xxx”

The announcement marks a happy chapter for Fry, who has spoken publicly about his loneliness after previous relationships have ended.

The couple reportedly made a formal application to marry at a register office in Dereham, Norfolk, Fry’s home county, on 23 December.

Fry’s personal assistant said the planned marriage was a private matter, adding: “Stephen Fry is very happy and proud to say that he has set the wheels in motion for a wedding sometime in the future, but no date has been set due to a busy work schedule.”

In 2010, the actor separated from his partner of 14 years, Daniel Cohen, whom Fry credits with “saving” him during periods of severe depression. He then reportedly began a new relationship with Steven Webb, 27 years his junior. But Fry was apparently single again by the summer of 2013, when he wrote in a blogpost about how he felt “lonely in a crowd of people who are mostly very nice to me. Loneliness is the most terrible and contradictory of my problems. I hate having only myself to come home to.

“It’s not that I want a sexual partner, a long-term partner, someone to share a bed and a snuggle on the sofa with – although perhaps I do and in the past I have had and it has been joyful. But the fact is I value my privacy too. It’s a lose-lose matter.”

Fry, who has bipolar disorder, has also spoken publicly about attempting suicide as recently as 2012.

The comedian Robert Webb, who starred in Channel 4’s Peep Show, was one of the well-wishers who wrote to Fry on Twitter: “Ooh! Congratulations Stephen. Marvellous news x”.

@stephenfry ooh! Congratulations Stephen. Marvellous news x — Robert Webb (@arobertwebb) January 6, 2015

The musician James Rhodes, a friend of Fry, added: “Isn’t love the absolute BOMB :) You guys are such an ace couple x”.

The broadcaster replied to hundreds of congratulatory messages from fans on Twitter by saying their “adorable tweets are bringing me close to sobbing”.

According to documents on display in Norwich, the wedding will take place in a local register office. No date has been set for the ceremony.

Fry first found fame as part of a double act with Hugh Laurie after the pair met at university.

They appeared in their own long-running show as well as in the Blackadder series and a TV adaptation of the Jeeves and Wooster novels.

He has also produced a string of documentaries, novels and memoirs and hosts the panel show QI.