Gavin and Stacey actress Margaret John has died at the age of 84, it has been announced.
John, who also starred in the BBC Wales comedy High Hopes, died in hospital in Swansea after a short illness.
The actress, who received a Bafta Cymru lifetime achievement award in 2009, starred as neighbour Doris in the Barry-based BBC hit comedy.
Gavin and Stacey co-star James Corden Tweeted: "A great actress and an incredible lady. She will be missed."
Mathew Horne, who played Gavin, sent this Twitter message: "Really sad to hear Margaret John has passed away. She was such a good woman and so fun to work with."
Rob Brydon, who played Uncle Bryn in the series, also wrote: "Just heard the terribly sad news that Margaret John has passed away. What a wonderful person she was, everyone on G&S adored her."
Joanna Page, who was Stacey in the hit series, said: "Margaret was a warm, kind, cheeky, fun and beautiful lady. She was an incredible actress and it was an honour working with her. I'll truly miss her. All my thoughts are with her family."
Fellow actress Ruth Madoc said: "It's very sad news. Margaret John was a great Welsh icon - and an era has passed away with her.
"She had a wonderful sense of humour. We were part of the Taffia in London in the 60s - and I always looked up to her."
John appeared on stage in Calendar Girls in the Wales Millennium Centre in Cardiff last summer.
Paying tribute, the venue hailed her a "national treasure".
Heritage Minister Alun Ffred Jones said: "She was one of our best-loved actresses and there was always a touch of humour or a glint of wickedness about her.
"It's a sad day but it was a life lived to the full and we are all the richer for having her."
BBC Cymru Wales director Menna Richards praised John as "a cornerstone of the television and radio industry in Wales".
"Her vitality, energy and enthusiasm endeared her to generations of people and I'd like to pay tribute to her for the immense pleasure she gave to her many fans in Wales and beyond," she said.
A tribute programme, Margaret John: National Treasure, charting her career which spanned 50 years, will be shown on BBC One Wales on Sunday, 6 February, at 10.00 BST.
Her last appearance on screen was in the new S4C drama Alys on Sunday night.
Although known in recent years for her colourful one-liners in Gavin and Stacey, the Swansea-born actress had a long and distinguished career.
Born in Swansea, John left drama school in 1950.
Her earlier career included a brief spell in Coronation Street in 1965 as well as a role in Z Cars, Dr Who, Dixon of Dock Green and Emmerdale Farm.
John also starred in David Schwimmer's British film comedy Run Fatboy Run (2007) and enjoyed recent appearances in medical dramas Casualty and Doctors, and the Welsh-set BBC drama Framed with Trevor Eve and Eve Myles.
The late 1970s saw John star as Marian Owen in another soap opera, Crossroads (famous for its wobbly sets), and from 1984 she starred in medical drama The District Nurse as Gwen Harris alongside fellow Welsh actor Nerys Hughes.
She played the part of Elsie 'Mam' Hepplewhite in BBC Wales comedy High Hopes between 2002 and 2008, starring alongside Robert Blythe and Boyd Clack.
John recently had a role in spoof valleys film comedy A Bit Of Tom Jones and an appearance in the second series of BBC Three drama Being Human.
Last year the actress lent her support to a £20m scheme to reduce social loneliness among the elderly people in Wales.
Her agent, Gemma McAvoy, said: "Margaret worked tirelessly for charity; always happy to give her time and boundless energy to help others.
"She completed 'the mile' for Sport Relief; performed with Only Men Aloud and stuffed money into John Barrowman's trousers for Children in Need and played drums for the Gavin and Stacey Comic Relief Barry Islands in the Stream sketch.
"Locally, Margaret worked with the PDSA, the George Thomas Hospice and was the face of the Big Lottery Fund AdvantAGE campaign which aimed to create social opportunities for older people, to name but a few examples.
"Professionally, Margaret was just as generous; consistently giving her time and expertise to help up and coming filmmakers."
A tribute programme, Margaret John: National Treasure, will be shown on BBC One Wales on Sunday, 6 February, at 10.00 GMT.
Meanwhile, on Wednesday 2 February, at 19.00 GMT The Diaries of Mrs Bebb, a bittersweet comedy starring Margaret John as Mrs Bebb will be broadcast on BBC Radio Wales.