Police community Support Officers (PCSOs) are set to go on strike on New Year's Eve when alcohol-fuelled revelry means they are most in demand.
An as-yet unknown number of civilian police officers in London are set to walk out in a dispute over pay, on the night of the year when high spirits may easily spill over in to public drunkenness and anti-social behaviour.
Scotland Yard has no idea precisely how many PCSOs will fail to turn up for their shift on NYE, meaning police chiefs could be left scrambling to fill gaps in the service.
Also poised to join the walkout are 999 call handlers who field emergency calls from members of the public.
Behind the planned strike is the Public and Commercial Services Union, which has 7,500 members in the Met Police, out of a total workforce of more than 14,000 people. Together with a planned walkout by fire fighters, it could spell chaos for emergency services in London on New Year's Eve.
PCS general secretary Mark Serwotka said: "The Met Police is not short of money, it does not need to force pay cuts on low-paid staff who help to keep London safe."
Scotland was trying to play down the potential impact of any strike on services by pointing out 1,150 staff members voted for strike action, which accounts for less than one in 12 of all employers. A spokesman said "tried and tested" plans were in place to soften the affect. "These ensure that critical functions performed by police staff are performed by police officers who are fully trained in those roles," he said.
It is expect duties normally performed by civilian police staff will be taken on by full police offciers, who are forbidden by law from going on strike. Requests for leave on New Year's Eve have been turned down in a bid to minimise disruption to frontline services.
A spokesman said: "We have tried and tested business continuity plans for all eventualities, including industrial action. These ensure that critical functions performed by police staff are performed by police officers who are fully trained in those roles."
Civilian police staff are walking out after a demand for a six percent pay rise by the PCS was turned down. Civilian staff were offered 1 percent, in line with the pay cap in place across the public sector.