Ventajas
It's very dependent on the department, but my work-life balance was excellent and I could wfh most of the time with no questions asked. Most of my team with family abroad was able to work from their home countries for a while. The clients were interesting and the colleagues I met in the London office were very friendly and diverse, although it depends on the crowd/department you gravitate around.
Desventajas
Poor pay compared to market rates, minimal salary increases when they were handed out. No training or development opportunities/budget. Saw a few instances of nepotism at junior levels. HR was not able to keep matters confidential when involved in grievances which created huge issues at team level. Senior leadership is not diverse and internal career progression is extremely slow and unprofitable, especially if you start at band F.