as part of the show's opening credits, and have included shots of the Square Mile and Canary Wharf financial districts, as well as the 180-metre Gherkin, HSBC Tower, One Canada Square, the Citigroup Centre, and the Shard; such locations are not used for filming unless a task involves visiting the site. Candidates and tasks Filming of an episode can usually take a considerable amount of time to be done and as such, each task is usually filmed back-to-back, rather than weekly as it appears in the broadcast schedule for a series. For each episode, four television crews are used to follow the candidates during a task, and often are focused on picking up on mistakes and issues between candidates, than on their overall performance. The final edit of an episode often trims down a task that took 1–3 days to be done, to fit it within approximately about half of what will be televised for that episode, meaning candidates may appear to make minimal contributions when in reality they made more, while others may not feature as much if Sugar or his advisers feel they did well and completed their duties, as emphasis is often put on moments that can be entertaining for audiences. Often the filming of an episode can hamper the efforts of candidates in a task, due to film crews usually having to get filming permission first from the respective owner of a store or establishment, which can often be a time-consuming and cumbersome process as a result, whilst the strict rules of the BBC on product placement and advertising mean candidates have to approach businesses with care when asking them for help. Owing to the need for secrecy during the two months of filming, all candidates are made to sign a confidentiality agreement which prohibits all, but a few confidants nominated by them, to be told of where they will be during that time, which remains active after filming until the series has started broadcast. As part of this agreement, all contact with the outside world is restricted to a high level – each candidate gets a limited phone call once a week, has no access to newspapers, television or internet, and is required to hand in any electronic communication equipment they have (i.e. mobiles) before they begin. In addition, all candidates are made to remain in their accommodation throughout filming except when they must head