Planning to take the kids to the Tower of London the second week-end of October half-term, probably the Saturday. Thought we would book online in advance to reduce queuing time. Would appreciate advice as to whether we need to get there early (and, if so, how early) to avoid horrendous queues. Obviously it's going to be busy around that time, but there's a difference between "busy but still enjoyable" and "so busy it's hard to see anything". Would be interested to know which kind of busy it's likely to be.