The security forces are reviewing public safety and issuing advice to the public in the South after the bombing at Manchester Arena last night.
People are being advised to go about their ordinary lives, but at the same time to be on alert and to report any suspicious incidents.
Video may contain distressing scenes
People in the Thames Valley are being urged to stay vigilant this summer after the terrorist attack in Manchester.
There have been no specific threats, but the region is hosting a wide number of major events over the next few months, including the Reading Festival and Common People in Oxford, which is being held this weekend.
Security is already tight at these events and officials are telling those attending to stay aware but not to panic.
Organisers for Common People say that they are liaising with police ahead of the festival.
Reading FC are playing in the Championship play-off final this Monday at Wembley Stadium, with thousands expected to attend.
The English Football League (EFL) and Football Association (F.A.) say that there will be an "enhanced" security operation at the match but that there have been no specific threats.
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A vigil has been held to remember the three victims of the terror attack in Reading.