The Moody Blues star Ray Thomas has died suddenly at the age of 76, his record label has confirmed.
The flautist and vocalist died on Thursday at his home in Surrey.
Announcing Thomas' death "with profound sorrow and sadness", Cherry Red Records and Esoteric Recordings said: "We are deeply shocked by his passing and will miss his warmth, humour and kindness.
"It was a privilege to have known and worked with him and our thoughts are with his family and his wife Lee at this sad time."
Moody Blues bass guitarist John Lodge tweeted: "Ray and I have been on this magical journey through life together since we were 14…two young kids from Birmingham who reached for the stars…and we made it together.
"El Riot you will always be by my side."
Thomas revealed on his website in 2014 that he had been diagnosed with prostate cancer.
He said he received his diagnosis in 2013.
"My cancer was inoperable but I have a fantastic doctor who immediately started me on a new treatment that has had 90% success rate," he wrote.
Ray and I have been on this magical journey through life together since we were 14…two young kids from Birmingham who reached for the stars…and we made it together. El Riot you will always be by my side #moodyblues@rockhall#Moodiescruise
— John Lodge (@JohnLodgeMusic) January 7, 2018
"The cancer is being held in remission but I'll be receiving this treatment for the rest of my life."
Thomas was born in Stourport-on-Severn, Worcestershire, on 29 December 1941.
He started out in blues and soul groups in the 1960s and later formed The Moody Blues alongside Mike Pinder, Denny Laine, Graeme Edge and Clint Warwick.
The rock band went on to have successful hits including Go Now, Nights In White Satin and Question.
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Thomas also enjoyed solo success with albums From Mighty Oaks and Hopes Wishes And Dreams.
The Moody Blues are to be inducted into the Rock & Roll Hall of Fame in April.