Documents to show immigration officer at UK airport

[MSJAKA]

We have gone through most of the process of a spouse visa application for my husband who lives in Pakistan, and have received the original documents back. I am going to send the original TB certificate back to him, as it states you need to keep it in hand luggage to show to the immigration officer on arrival at the UK airport, but what other documents do they ask to see? Thought I'd check before sending, in case I need to put anything else in the envelope. I did try searching, but didn't manage to find anything.