I'M WATCHING YOU, FLETCHER! CONTAINS EXTREMELY LARGE SPOILERS
I'd always thought that this was Island ON Fire, since it's a Hong Kong action film that came out around the same time as City On Fire, School On Fire, Prison On Fire, Outside Toilet On Fire and so on. Turns out it's quite definitely OF, as in Chariots. And given that the average Hong Kong action movie has a raft of alternative titles, it's perhaps surprising that this hasn't been renamed to fit in with the other movies, even though it's entirely related to it. One of those titles is Jackie Chan Is The Prisoner, which would be a bit of a cheat because  even though he's first billed, Chan is very much in a supporting role,  since almost the entire film is set in prison, half the cast are prisoners, and  Jackie Chan doesn't wake up in a strange village in Wales and he isn't forced to play absurd mind games with a mysterious and unseen Number One.
The Island Of Fire of the title is Hong Kong, where a cop (Tony Leung) goes undercover in the prison to investigate how an executed convict's finger turned up at the murder of a veteran police officer looking into high-level police corruption. Also in prison is genial serial-escaper Sammo Hung and wrongly convicted Jackie Chan, a pool champion who accidentally killed a gangster in a fight after not taking a bribe to lose. The villains - because we are on the side on the inmates here - are the oppressive and sadistic wardens and guards who delight in the suffering and brutality inflicted on their charges. In fact there's so much focus on the viciousness of the prison and the day-to-day battle to survive, that the film almost forgets that there's also a plot about high-level police corruption to sort out as well, and the mystery of the long-dead assassin. When our heroes are scheduled to be executed, things become much clearer.
Porridge it isn't. Island Of Fire may be a late 80s/early 90s Hong Kong action movie with Jackie Chan and Sammo Hung but there's little fun to be had and very little in the way of the immaculate slapstick you'd expect. It's far grimmer than that - the prison bullies cook the quiet geeky convict's pet mouse and give it to him for his dinner, Sammo kicks a dog during one of his escape bids - and the fight scenes don't conclude with people dusting themselves off going "ouch!" but being carted away to the sickroom covered in bruises. Nor, for most of our heroes, do events end happily: the film is quite willing to bloodily kill them off in the final reel.
Not to say for a second that I didn't enjoy it, although it was more downbeat than I was expecting. It's still quite well made and the action scenes are as dazzling as ever. Sometimes the melodrama can be a bit mawkish - Sammo Hung keeps escaping only so he can spend a few beautiful hours with his son before being recaptured, and as soon as he promises to be there for New Year's Eve, you know he won't - but that's just the culture difference and it's always going to happen. Still worth a watch; I thought it was pretty good.