Microfr Support Defender Virus Scam

My father, aged 86 and using Windows 10 with the latest Norton, was looking at my local newspaper website in the UK. He went and poured a drink and upon returning to his PC, the was a complete screen notice proporting to be from Microsoft regarding a serious virus on his PC. Told not to restart or anything, but contact Microsoft Support on a given number.
I called my son, who has many years experience in IT. He came to mine and decide it was a attempted hack. He rang the number, which sounded as though it got redirected. A foriegn man answered stating he was a technical engineer at Mocrosoft. My son asked how could he be sure. The man said it again and my son advised he was an experienced IT user and made it clear that he did not believe him. Then hung up. The man called back and asked why he did not believe him and my son said that he would call Microsoft and hung up. A few minutes later, the man rang back and was abusive in his manner. My sone easily managed to log out and back in, after which the 'Warning' was no longer there. He the ran my Norton AntiVirus and a few other utilities and all is now fine.