Where to begin? Okay, deep breath... Diane Keaton and Robert De Niro used to be married, but they are now happily and civilly divorced, and De Niro has since remarried to Susan Sarandon. Keaton and De Niro have three lovely kids; the anxiety-ridden Katherine Heigl, the 29 year old virgin Topher Grace, and the adopted-from-Columbia Ben Barnes. Barnes is about to get married to Amanda Seyfried and under the watchful eye of Barnes' old-school Columbian birth-mother, Seyfried's right-wing racist parents, and their bible-bashing minister Robin Williams, he asks his parents to do him a favour. Just for the few days that everyone is in town, can Keaton and De Niro pretend they never got divorced and are still happily married? Simple! You got all that?

Yes, this is the kind of set-up that only exists in movies, featuring the kind of family that only exists in movies. English-born Barnes playing a Columbian with three different mothers? Grace is a handsome doctor who's waiting for love before having sex until he clamps eyes on Barnes' Columbian sister and promptly all ideas of chastity are thrown to the wind? The plot is a weave of the likes of The Birdcage and The Family Stone and countless other rom-coms you've seen that involve a family coming together for an event, and how writer/director Zackham managed to bag such an enviable cast can only be explained by some sort of blackmail.

It's not that the movie is bad; it's just that it's run-of-the-mill, so averag and so utterly forgettable. Just like its blandly blah title, The Big Wedding has no real surprises in store for us. Unless you consider some naughty language - De Niro says the C-Word! - and some mild conversations about sexual behaviour to be surprising.

Nobody here turns in a bad performance - in fact, Heigl and De Niro have some nice father/daughter scenes, and Williams does a far better job at being a funny priest here than he did in Licence To Wed - but even as you're watching the movie for the first time, the sense of déjà vu is painfully overpowering. It's a harmless rom-com that's not that funny or that romantic, only RSVP if you have nothing better to do that day.