But he has been reunited with his former Ospreys coach Lyn Jones at the Exiles, following ill-fated stints at the Blues, Toulon and Saracens.
"I sincerely hope and believe he can draw a line under that period and move forward with London Welsh," said Jones.
"What's important for Gavin is that he concentrates 100% on his game and learning how to become the best he can possibly be again"
The move to London Welsh is latest attempt by Henson to kick-start his career following several tumultuous years.
He took indefinite unpaid leave from the Ospreys in 2008 before being released in October 2010 to join Saracens.
He then joined French Top 14 side Toulon in February 2011, after only four months at Saracens, but that move was also short lived and he left at the end of the season
Henson, who toured New Zealand with the Lions, making four appearances Down Under, made an international comeback in 2011 but saw his hopes of playing in a first World Cup once again dashed by injury.
After recovering from the dislocated wrist he suffered against England he joined Cardiff Blues but he left following an incident on a flight from Glasgow in February.
But Jones, who has also brought Sonny Parker to the Premiership, reckons Henson can once again fulfil his potential.
"Gavin has a great talent but over the past three or four seasons he has not realised his full potential for a number of reasons that are well documented," added Jones.
"He can add a great deal to our game and we can also do a lot for him.
"We all appreciate the skills that he can bring to a game but what team-mates and coaches will be looking for is consistency of that ability.
"That's the challenge for Gavin, to hold his concentration fully on rugby as he did when he started his career, when rugby was first, second and third on his list of priorities."
Henson will become just the latest Lion to represent the famous club. They have contributed 18 Lions in previous years including seven to the 1971 tour of Australia and New Zealand.
One of those, John Taylor, is now the club's managing director and he was delighted to sign Henson.
"We are obviously delighted to have been able to sign a player of Gavin's pedigree," said Taylor.
"He is the first to admit things have gone a little haywire over the last few years but he has impressed on me that he still feels he has a lot to prove as a rugby player and is determined to ensure he is not remembered as somebody who never fulfilled his great potential.
"I am confident he will fit in well here and it is obvious he cannot wait to get back to what he does best - playing rugby."