Grammy award-winning singer/songwriter George Michael was taken to hospital by ambulance after collapsing at his mansion in North London.

A worried friend called for the ambulance at 8am on Thursday May 22, the London Ambulance Service confirmed.

In an unusual twist, witnesses have reported it was four hours after their arrival that the ambulance crew took the singer to hospital for “emergency treatment”.

The controversial singer, who battled a severe case of pneumonia in 2011, has only made one announcement so far via his publicist saying, “George Michael was in hospital for routine tests but there is nothing further to say”.

Fans have expressed concern for the 50 year-old singer’s health after a series of health issues and incidents surrounding his regular use of cannabis, which he claimed he had stopped using in March.

The latest bizarre incident involved Michael falling out of a moving car on the M1 motorway in London, while he was sentenced to an eight week prison sentence in 2010 after he drove his Range Rover through a Snappy Snaps photo shop in North London. He was given a five year driving ban after he pleaded guilty to driving under the influence of drugs.

Earlier this year, the singer/songwriter and producer proved his ongoing popularity with the British record buying-public when Symphonica, his first album since 2004’s critically-acclaimed Patience, went to number one.

Watch the video for George Michael’s latest single “Feeling Good” below.