Wedding guest attire for my husband

We're going to our first UK wedding wedding this weekend... does he have to wear a suit?  It's around 40 people and afternoon wedding... he's hoping to just wear a shirt and tie with dress pants....now that I think about it he should probably wear the suit.

Any thoughts? 

UK weddings (the ones I've been to, anyway) have been no different from US weddings, dress-wise.  He should wear a suit.

Definitely needs to wear a suit. Other people will probably talk about him and be really judgemental if he doesn't. That's what I've experienced anyways.

Definitely a suit unless the invitation indicates otherwise.

definitely suit

If he doesn't own a suit, a sweater over a dress shirt and tie is probably fine. One guy came to my wedding in a tux and I didn't notice (though I did notice his saddle shoes) any more than I noticed that my aunt and one of my friends wore the same dress (what are the odds of that? - they live in different countries!).