Fantabulosa sees Michael Sheen, who played Tony Blair in Channel 4's The Deal, take on the role of Williams, best known for his appearances in 22 Carry On... films.
Made in-house, the 80-minute programme, written by Martyn Hesford, uses Williams's own diaries as the basis for the story, portraying the tragic and unbalanced life behind his publicly cheery demeanour. The programme leaves the question open ended of whether Williams committed suicide or not.
"At the time he allegedly took his own life everything was going wrong," said producer Ben Evans. "His mother was suffering from Alzheimer's and he was in great pain. But the only person who knows whether he committed suicide is him."
Directed by Andy de Emmony, the programme is executive produced by Richard Fell and Sally Woodward, and was commissioned by BBC4 controller Janice Hadlow.