Police are facing "the biggest and most complex event ever staged in Scotland" with COP26 coinciding with Bonfire Night and Hallowe'en carnage, it was warned.

World leaders including US President Joe Biden, Pope Francis and Queen Elizabeth will be in Glasgow for the U.N climate conference in November.

But Police Scotland and other 999 crews face their biggest annual pressure on November 5, while Hallowe'en revellers cause chaos.

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Reinforcements of 10,000 officers are being draughted in from the four nations to back up the stretched police force.

Chair of the Scottish Police Federation, David Hamilton, said: “We will do our best and do everything we can, but it is going to be tight for us.

“Police will start at the top of the priority list and work their way down.

“Whilst we continue to push the service into ensuring that everything that can be done to prop up the service is done, the inconvenient truth is – there just aren’t enough police officers.”

Vowing the federation would do everything possible to “prop up” the force during the summit, Mr Hamilton warned disruption on key dates in October and November would “stretch policing capacity to and beyond the absolute limit”.

Mr Hamilton said: “November 5 is an exceptional date for police demand in any ordinary year.

“The last three years have been very challenging and we don't expect it to be any different this year.

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"A lot of work is getting done to support the frontline officers from back office posts as much as possible.”

The next day will see as many as 200,000 descend on Glasgow, to attend a UN-backed climate protest, which cops fear could be "hijacked".

Police Scotland has been engaging with various groups, including Extinction Rebellion, to ensure it goes smoothly.

More than 10,000 UK officers are expected to arrive in Glasgow in the days leading up to COP26, and around 2,500 Scottish officers are receiving extra training in how to manage large protests.

The force has also cancelled all holiday leave for officers during the summit to meet the enormous pressure.

Glasgow Times:

Bernie Higgins, the assistant chief constable co-ordinating the COP26 police response, said "the significance and scale of this event should not be underestimated".

He said: "COP26 will be the biggest and most complex event ever staged in Scotland.

"This will necessitate the largest mass mobilisation of police officers that has taken place in the UK in many years."