Sir Elton John was ''very upset'' about his feud with the late George Michael.

The pair famously fell out over George's wild lifestyle and whilst they were able to rekindle their friendship before George's untimely death on Christmas Day (25.12.16), the whole feud left the 'I'm Still Standing' hitmaker feeling incredibly sad.

Mutual friend Paul Gambaccini told the Daily Mirror newspaper: ''Elton was very upset, we exchanged emails.''

The pair had been friends for sometime, even uniting to release a duet of 'Don't Let the Sun Go Down on Me' in 1974. However, things went downhill from there for their friendship as George continued to uphold his wild lifestyle.

Things came to a head in 2004 when Elton said George was in a ''strange place'' and claimed there was a ''deep-rooted unhappiness'' in his life.

And in response, George hit back: ''Elton knows very little about George Michael and that's a fact. Most of what Elton knows about my life is limited to the gossip he hears on the gay grapevine.''

It is believed the pair fell out because George refused to let Elton help him curb his wild lifestyle.

In 2009, George fired back: ''He [Elton] will not be happy until I bang on his door in the middle of the night saying, 'Please, please, help me, Elton. Take me to rehab.' It's not going to happen ... Elton just needs to shut his mouth and get on with his own life.''

However, the pair seemingly built bridges and were ''getting on brilliantly'' once again.

A source said in 2011: ''They have been seeing each other quite a lot. The feud is finally over. George and Elton are getting on brilliantly again and everybody is thrilled.''

When George passed, Elton publicly praised the 'Careless Whisper' hitmaker for being the ''kindest [and] most generous man''.

Speaking during a radio interview last month, he said: ''I wanted to do a little tribute to him on the show because not only was he a good friend, but he was probably one of the most brilliant songwriters this country's ever produced, and certainly one of the best vocalists ever. One of the best in the world ...

''He was the kindest, most generous man, and did it without wanting any publicity. I've seen him being so kind to so many people. I'll miss him so much for his music but more than anything for his humanity.''