Metropolitan Police Chief Cressida Dick talks to instructors during a police crowd control exercise on a purpose built street at the Metropolitan Police training centre in Gravesend.

Mounted police move through a purpose built street to disperse 'protesters' during an exercise at the police training centre in Gravesend.

Officers at a police crowd control exercise conducted on purpose built streets at the Metropolitan Police training centre in Gravesend where several purpose-built, false fronted, streets have been bui...

Police officers don their riot gear during public order training at the Metropolitan Police's training centre in Gravesend.

Police officers don their riot gear during public order training at the Metropolitan Police's training centre in Gravesend.

Metropolitan Police Chief Cressida Dick talks to officers during a police crowd control exercise on a purpose built street at the Metropolitan Police training centre in Gravesend.

Riot shields piled up behind the false front of one of the 'streets' built at the Metropolitan Police training centre in Gravesend to help training for real world public order situations.

Metropolitan Police Chief Cressida Dick looks on as instructors brief officers during a police crowd control exercise at the Metropolitan Police training centre in Gravesend.

Police officers wearing riot gear during public order training at the Metropolitan Police's training centre in Gravesend.

Metropolitan Police Chief Cressida Dick looks on during a police crowd control exercise at the Metropolitan Police training centre in Gravesend.

The remains of petrol bombs burn on the road during public order training at the Metropolitan Police training centre in Gravesend where several purpose-built, false fronted, streets have been built to...

Metropolitan Police Chief Cressida Dick at the Metropolitan Police training centre in Gravesend.

Metropolitan Police Chief Cressida Dick at the Metropolitan Police training centre in Gravesend.

Metropolitan Police Chief Cressida Dick at the Metropolitan Police training centre in Gravesend.

Metropolitan Police Chief Cressida Dick at the Metropolitan Police training centre in Gravesend.