Sir Cliff Richard recalls final phone call with Olivia Newton-John in emotional tribute

Sir Cliff Richard has paid an emotional tribute to his good friend Olivia Newton-John, following her death at the age of 73.

The musicians had a close relationship since they first met in the '70s, with the legendary singer previously describing her as his "soulmate" when writing in his memoir.

Now, Richard has broken his silence and is among the dozens of high-profile celebrities honouring the Grease star's incredible life.

Opening up about their final phone call, the 'Devil Woman' hitmaker admitted he never thought he would be writing a memorial to her just three weeks later.

Taking to social media, he began by admitting: "I find myself at a loss as to what to say ...

"I’m just one of an army of lucky people who knew and loved her. How could we not love her? She was gorgeous, gifted and had a heart of Gold ...

He continued: "When she was first diagnosed with cancer Livvy put her career on hold for years. Why? Because she wanted to inspire other sufferers to do as she did…fight the ugly disease, although she said in one interview that she wasn’t in a battle with cancer just that she had something that she simply wanted to get rid of!

"Olivia always had an up-beat approach to life. Only three weeks ago I was on the phone to her, and she was her bright positive self and I never thought for one moment of that call that I would be writing this and acknowledging her death. I hate that word!

"From now on I will only believe that our gorgeous Olivia simply stopped living. I will miss her. The world will miss her, so let’s all keep her alive in our hearts and memories.

He signed off his last message to his dear friend with the words: "God bless you Livvy. Rest in Peace…… Cliff xxx."

Newton-John died Monday morning at her ranch in Southern California, where she was surrounded by family and friends.

While a specific cause of death has not yet been revealed, a source close to TMZ reported that "she lost her battle to metastatic breast cancer."

The 'Physical' hitmaker is survived by her husband, John Easterling, who shared the news of her death on her official Instagram account, and her daughter, Chloe.