The Krios of Sierra Leon Exhibition, at the Museum of London:
Current opening times: 1.30am-3.30pm, Monday-Friday and from 10am-6pm on Saturday and Sunday.
You now need a free ticket, which you can book in advance using the calendar on the Museum of London page.
Advance ticket booking is highly recommended, but there will be a limited number of walk-up tickets available on the day for spontaneous visits. 
Call 020 7030 3300 to check ticket availability before you visit.