The 62-year-old actor has reportedly checked into a treatment center to undergo specialised treatment for addiction.

It is being called a preventative measure by his rep, not because he has fallen of the wagon, but because Williams wants to maintain his long-term sobriety.

A spokesperson for Williams has stated: "After working back-to-back projects, Robin is simply taking the opportunity to fine-tune and focus on his continued commitment, of which he remains extremely proud." 

Williams has openly struggled with alcohol and drug addiction for decades. He gave up cocaine and alcohol in the early 1980s after the death of his friend, comic John Belushi.

Williams remained sober for 20 years before falling off the wagon again.

The actor has remained sober since a rehab stint in 2006.

Williams is expected to stay several weeks at the treatment centre.