A couple of friends of mine and I are spending a day and a half in London at the end of October. All but one of us have been there before, and the Eye is on our "definitely do" list. We're thinking about getting advance tickets, but aren't sure when would be the best time to go. I was thinking dusk (5:30?) would be beautiful, but we only have one evening free and were thinking about going to the evening service at St Paul instead. We had thought about around 2pm, but my friend heard that it can get foggy that time of day (have no idea how true that is). Any thoughts?

< but my friend heard that it can get foggy that time of day >

Maybe 50 years ago.

As for when to go - when it's a nice day. I wouldn't book ahead as British weather is too unpredictable

I've been on the Eye a couple of times and I enjoyed the nicest views at twilight!

You shouldn't need to book ahead - and the weather is more important than the time of day. late afternoon/dusk is terrific - but not so hot if it is rainy/low ceiling. Clear in the a.m. vs rainy at sunset - no contest.

So wait until you are there and check the local weather forecasts.

The last couple of times we went on the Eye there was essentially no line or much of a wait to get on. Probably less than 1/2 hour from getting into ticket line to entering a pod.
Views are great during the day and during the evening. Mostly just depends on the weather. A clear day or clear evening would be best.
I can't think of a bad time to go.