Brits could be encouraged to work from home this week as London fills up with well-wishers hoping to see the Queen’s coffin.
The late monarch will lie in state in Westminster Hall between Wednesday and Monday, when her funeral is due to take place.
Queues to see the coffin are expected to exceed 20 hours and stretch for three miles.
Transport chiefs have warned that London will experience “unprecedented travel demand” and public transport users are being advised the city will be “exceptionally busy”.
Tube stations might even have to close to stop overcrowding.
Today a spokesperson for Liz Truss said commuters may want to “change their working patterns accordingly”.
But they added that “not everyone will have that ability”.
It will ultimately be up to employers to decide whether staff can work from home rather than the office.
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The last person to lie in state was the Queen Mother in 2002.
Around 200,000 people came to Westminster Hall to pay their respects, but Whitehall bosses expect that number to be way higher this time around.
In fact, it could be closer to the million mourners who filed past Pope John Paul II when he lay in state in Rome in 2005.
The queue route will be lined with extra portable loos and water stations to ensure the public are catered for on their way towards Parliament.
Mourners will pass through airport-style security and only small bags are permitted.
Medics at nearby Guy’s and St Thomas’s hospitals are on standby in case those in the queue fall ill.
Planners, who have been following the Operation London Bridge protocol, have identified a park next to Tower Bridge as the starting point for the queue.
It will then move the length of the South Bank of the Thames, passing London Bridge, Blackfriars Bridge, the Globe Theatre, Tate Modern and the London Eye.
Anyone with luggage will have to stop on the route and leave it in a park by Lambeth Palace before re-joining the queue.
Tube passengers are being advised avoid Green Park station due to the masses of crowds looking to visit Buckingham Palace.
A special service will run on the Elizabeth line Paddington and Abbey Wood on to ease the pressure on other parts of the transport network.
Network Rail chairman Sir Peter Hendy said: “The transport industry is working hard to help people pay their respects in London and across the United Kingdom.
“Please make sure you check before you travel as we expect the road and transport networks to be busy.”