Pros
The people are very friendly and fun to chat with. The managers pay attention to what you do all day and show their appreciation for the work you put in. There is always someone willing to help if you need it. Processes are clearly laid out and easy to follow. There is great job prospects, career growth and line managers will put you forward for roles they think you would be good at. The training programs are very good and post-training support is even better. The company feels like it is going places, and has the data to back up the claim. There is always something new to learn and you won't get bored doing the same things over and over again. The London office is in a great location and is not short of facilities for lunch time or evening fun.
Cons
A minority of departments lean more to the reactive than proactive work ethic but this is changing, slowly. The lifts keep breaking so sometimes you have to use the stairs. High level management tend to keep to themselves and their immediate subordinates. Due to the processes in place, simple changes can take time to complete and harder changes can sometimes carry on for months. Office politics have at times been handled unproffesionally.