The 36-year-old has reunited with his old band 15 years after he left and rumours claim a film is set to be made detailing his return.
A source said to UK newspaper The Sun: 'Cameras have been with them right through the last chapter of their lives. The lads really wanted this to be an honest account of what happened when they were making friends all over again.
'It wasn't easy and they've had to bare their souls more often than they planned. Mark had a lot of problems in his private life when he admitted to his drink problem and marriage difficulties.
'But it just showed how tight they are as a unit.'
Robbie recently released single Shame with Gary Barlow and his first single with the band, The Flood, is due out soon.