although public order is not the tsg's only role, it is certainly their most visible and well-known. like most police support unit vehicles, tsg vans are equipped with mesh window shields and officers are equipped with acrylic glass riot shields, visored 'nato' helmets, shin and elbow guards, along with fireproof coveralls when required. this level of protection allows them to deal with many violent situations, including riots, football violence and suspects armed with a variety of weapons. tsg officers are trained to a higher standard of operational readiness in their public order role than most other police support units outside london; tsg training is refreshed every five weeks as a matter of routine. exercises are conducted predominantly at the mps specialist training centre in gravesend, kent, though other sites are used as required, and encompass all public order scenarios; officers will undergo extensive riot training including being petrol bombed in large-scale engagements, prison clearance tactics, football stadium scenarios, night club scenarios, aircraft, rail and various 'angry-man' scenarios, as well as additional specialist training. tsg units spend considerable time training with other specialist police teams as well as certain military units. also, if a siege situation is present, but firearms are not involved, tsg will often be deployed to counter the threat. reflecting this role the unit's former head, commander michael johnson, was tactical commander for the london 2012 olympics.