Gogglebox's Leon Bernicoff has passed away, aged 83.
It's understood Leon died in hospital yesterday (Saturday, December 23) following a short illness.
The retired teacher and wife June have appeared on the Channel 4 series since the first show back in 2013.
In a statement Channel 4 paid tribute to Leon's "unique personality and sharp wit".
They said: "It is with a heavy heart that we announce the sad news that after a short illness Gogglebox's Leon Bernicoff passed away in hospital earlier today.
"Leon and his wife June were the first members of the public to be cast for Gogglebox back in early 2013, and they soon grew to become much-loved voices during the course of the show's 10 series to date.
"Leon's unique personality and sharp wit endeared him to fans of the show, as he contributed fully to Gogglebox's reputation as a programme full of warm humour and unvarnished opinion.
"To those of us that knew him personally, Leon was a man of unwavering principles who exerted a distinct paternal presence both on and off screen. He will be dearly missed by the entire Gogglebox family; cast and crew."
Gogglebox creator Tania Alexander posted on Twitter on hearing the news: "So deeply saddened at the passing of our dear, dear Leon. He was and always will be the grandfather of #gogglebox - an absolute star who always made me laugh with his sharp wit and unshakable opinions. Much love and strength to June."
Former Goggleboxer Scarlett Moffatt also spoke out.
"Words can’t explain what you meant to so many people. From your words of encouragement to me to the little DMs. Leon you were loved by so many. Sending my love to you and all of your family. @LeonAndJune," she said.
Leon's widow June has since tweeted: "Thankyou Folks for all your wonderful messages. Leon would have loved reading them & hearing how much he was loved. Goodnight & God Bless!"
The tragic news came just a day before Gogglebox's Christmas special, due to air tonight (Christmas Eve) at 9PM on Channel 4.
The special will be preceded by a tribute to Leon, Channel 4 has announced.