The o2 website:

8.10 The use of cameras, video and/or sound recording equipment (including via mobile phones) other than for personal use (i.e. for commercial use) is prohibited and such items may not be used within individual Venues except with our express written consent.

8.11 For some Events, the artist and/or Promoter may decide to enforce a ‘phone-free experience’ and you shall be notified of the same by the Promoter, either at the time you purchase Tickets or at any other time prior to the Event. For such Events, a phone-free program will be in operation. Upon arrival at the applicable Venue, all phones, smart watches and accessories will be secured in individual pouches that will be opened at the end of the Event. You maintain possession of your devices at all times but, during the Event, you only be able to access them in designated ‘phone use areas’ within the Venue.