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A police spokesman said officers have been working with management at the Grand Hotel, in Kings Road, since the phone call was received at 4.30pm on Sunday (September 10).
The police spokesman added: “An anonymous phone call was received at the hotel at 4.30pm on Sunday (September 10) alleging that there was an explosive device there.
“Hotel management decided to evacuate the hotel, a decision supported by the police, and the hotel was swiftly and safely evacuated.
“Thorough searches and enquiries are taking place to establish as soon as possible whether or not the call is a genuine one.
“Military ordnance disposal are attending as part of the search.
“Nothing untoward has been found at this time.
“In the meantime, roads and car parks in the immediate vicinity have been closed as part of the precautions.
“Drivers and pedestrians are advised that there will be some inevitable delays and diversions until the incident is safely resolved.”
A spokesman for The Grand Brighton said: “In response to a call made to the hotel; we have worked with the police and have taken the decision to evacuate the hotel as a precaution.
“In these times of heightened security we must be ever vigilant and ensure the safety of our hotel guests, team, suppliers and local neighbours.
“A full search of the premises and other local businesses is being conducted by the relevant authorities.
“We hope to return to normal service as soon as possible and apologise to any visitor who may have been inconvenienced.”
The Trade Union Congress – which is holding a conference at the Brighton Centre from today until September 13 – has been told to evacuate both the Grand Hotel and the Brighton Centre.
American restaurant The New Club – located opposite the i360 in King’s Road, Brighton – confirmed on Twitter that it has ‘been told to close by police due to what seems a serious incident at the Grand Hotel’.
A spokesman for the Churchill Square car park said on Twitter: “We can confirm our 24hr car park has been closed this evening following an incident nearby, which is being dealt with by the local police.”