Anniebach on the day that Ian Tomlinson died, the Met were dealing with six different protests in London.
According to Wilipedia "Over 5,500 Metropolitan police officers were deployed on 1 April and 2,800 on 2 April, at an estimated cost of £7.2 million ($11.3 million). Officers worked 14-hour shifts on average. According to a police focus group, they ended their shifts at midnight, were required to sleep on the floor of police stations, were not given a chance to eat, and had to be back on duty at 7 am. This was seen as having contributed to the difficulties they faced."
I have no idea why any of them would volunteer to do overtime in these circumstances - have you?