Brian Eno said he believes the last email sent to him by his friend David Bowie was a “goodbye”.

Bowie died on Sunday after a “courageous” 18-month secret battle with cancer, aged 69. A statement through his official social media account said he died “peacefully” and “surrounded by family”.

His long-time collaborator and friend Eno was one of many to pay tribute to the iconic glam rock singer, speaking with the BBC upon hearing the news.

“David’s death came as a complete surprise, as did nearly everything else about him. I feel a huge gap now.”

Eno explained that their most frequent communication was through email given that Eno resides in London and Bowie in New York with his supermodel wife Iman Abdulmajid and their daughter Lexi.

“We knew each other for 40 years, in a friendship that was always tinged by echoes of Pete and Dud… our connection was by email. We signed off with invented names: some of his were mr showbiz, milton keynes, rhoda borrocks and the duke of ear.”

David Bowie: Life in pictures Show all 30 1 /30 David Bowie: Life in pictures David Bowie: Life in pictures David Bowie in 1960s Dezo Hoffman/Shutterstock David Bowie: Life in pictures Davy Jones; life before David Bowie Getty David Bowie: Life in pictures David Bowie in 1964 Dezo Hoffman/Shutterstock David Bowie: Life in pictures David Bowie 'In Mime' at the Middle Earth Club, London, 1968 Ray Stevenson/Shutterstock David Bowie: Life in pictures David Bowie in 1969 I T N/Shutterstock David Bowie: Life in pictures David Bowie performing his final concert as Ziggy Stardust at the Hammersmith Odeon, London, 1973 Getty David Bowie: Life in pictures David Bowie in 1973 PA David Bowie: Life in pictures David Bowie, with his wife Angela (Angie) and his son Zowie, after receiving an award for his latest record "Ziggy stardust" in Amsterdam, 1974 AFP David Bowie: Life in pictures David Bowie in the 1970s Sunshine/Shutterstock David Bowie: Life in pictures David Bowie poses with a pig David Bowie: Life in pictures David Bowie's son, Duncan Jones, confirmed his death on Twitter Duncan Jones/Twitter David Bowie: Life in pictures David Bowie in the 1980s Everett Collection/Rex David Bowie: Life in pictures David Bowie gives a press conference presenting the Japanese movie 'Merry Christmas Mr. Lawrence' directed by Nagisa Oshima, during the 36th International Film Festival in Cannes, 1983 AFP via Getty David Bowie: Life in pictures David Bowie performs on stage during a concert in La Courneuve, 1987 AFP David Bowie: Life in pictures David Bowie during his concert in West Berlin, Federal Republic of Germany, 1987 EPA David Bowie: Life in pictures David Bowie shakes hands with Princess Diana, 1993 PA David Bowie: Life in pictures David Bowie autographs copies of his newest album 'Outside' at the grand opening of a Herald Square music store 26 September 1995 in New York AFP/Getty David Bowie: Life in pictures David Bowie performs at the Panathinaikos stadium in Athens during a rock festival, 1996 Reuters David Bowie: Life in pictures David Bowie and his wife, supermodel Iman smile as they pose for photos after Bowie received a star on the world famous Walk of Fame 12 February in Hollywood, 1997 Getty David Bowie: Life in pictures David Bowie getting ready to perform 'Earthling' at the Phoenix Music Festival in 1997 Pat Pope/Shutterstock David Bowie: Life in pictures David Bowie on stage performing during the Tibet House Benefit Concert in New York City, 2001 Getty David Bowie: Life in pictures David Bowie Meltdown concert at the Royal Festival Hall, London, June 2002 Rex David Bowie: Life in pictures David Bowie performing during his concert at the Stravinski hall stage of the Montreux Jazz Festival, in Montreux, Switzerland, 2002 EPA David Bowie: Life in pictures David Bowie in 'Last Call with Carson Daly' TV programme taping in New York, 2003 Startraks/Shutterstock David Bowie: Life in pictures David Bowie walks with his with wife Iman and daughter Alexandria (2) in New York, 2003 Shutterstock David Bowie: Life in pictures David Bowie performs on stage on the third and final day of 'The Nokia Isle of Wight Festival 2004' at Seaclose Park, in Newport, UK Getty David Bowie: Life in pictures David Bowie and Kate Moss at the 2005 CFDA Awards dinner party at the New York Public Library in New York City, 2005 Getty David Bowie: Life in pictures David Bowie and model Iman arrive to the Metropolitan Museum of Art Costume Institute Gala, Superheroes: Fashion and Fantasy, held at the Metropolitan Museum of Art in New York City, 2008 Getty David Bowie: Life in pictures David Bowie anf Tilda Swinton at the MoMA's 6th Annual Film Benefit in New York, 2013 BFANYC.COM/Rex David Bowie: Life in pictures Flowers are left below a mural of David Bowie on the wall of a Morley's store in Brixton on 11 January 2016 Getty

The duo worked on Bowie’s 'Berlin Trilogy' of albums from 1977 to 1979, including the iconic Heroes.

Their friendship spanned many years and in October, 2015 Eno shared pictures of Bowie’s wedding to Iman in Florence in 1992.

The pair later collaborated on Bowie’s 1995 album Outside, which Eno says they were recently reminiscing over through email.

“About a year ago we started talking about Outside… we both liked that album a lot and felt that it had fallen through the cracks. We talked about revisiting it, taking it somewhere new. I was looking forward to that.”

Eno last heard from Bowie a week before his death in a haunting email he now believes to be a poignant “goodbye” from his close friend.

“I received an email from him seven days ago. It was funny as always, and as surreal, looping through word games and allusions and all the usual stuff we did. It ended with this sentence: ‘Thank you for our good times, Brian. they will never rot.’ And it was signed ‘Dawn’.