Proof of Employment

I'm going to Newcastle just for a vacation, to see my boyfriend and to check out Newcastle University and meet with my advisor, but having read a few posts, I'm slightly concerned about refusal now. NOT that there should be any issue at all, as I've been granted entry twice already ('00 on a visitors visa, '02 student work visa thru BUNAC) with no forethought at all, but because I'm seeing my boyfriend while I'm visiting.

Anyhow, the point is I'd like to bring with me proof of employment. Can someone tell me what this would consist of? Is it a letter from my supervisor or boss?

Thanks in advance!   

Recent payslips, maybe? I know that's not proof of ongoing employment, but short of a letter from your employer saying as much, it's at least hard evidence of employment in the days before you travelled.

Last time I entered the UK as a visitor, I took a letter from my then-boss as proof that I was employed and that they were expecting me back on x date.  As it happens I didn't need to use it, but always a good idea to be prepared!