People will be able to pay their respects in Westminster Hall from 17:00 BST on Wednesday.
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People have begun claiming their spot to see the Queen lying in state at Westminster Hall – 48 hours early.
Vanessa Nathakumaran, from Harrow, was the first person to arrive on the south side of Lambeth Bridge, just after 12:00 BST on Monday.
The 56-year-old said she was “really happy” to be the first person in the queue after stewards told her where the line was set to start.
Barriers are being put in place along the route where crowds will wait.
People will be able to see the Queen lying in state from 17:00 on Wednesday until 06:30 on Monday, the day of her funeral.
Ms Nathakumaran, who is staying at a hotel in Lambeth so she does not miss the opportunity to pay her respects, said she was “really surprised as I was only just finding out the way and the layout, and in the end I found out from the stewards this is going to be the start.
“I thought I’ll stay from now on, I don’t want to miss my chance.”
She added: “Our part is to say a last goodbye, which is sad but I wanted to make sure I would be part of it.
“I started queuing up from today as I heard the queue is going to be very long, they’re expecting about three quarters of a million people will be coming at some point.”
Sixty five-year-old Anne, who did not want to give her surname, joined her two hours later, after she found out where the queue was when she saw Ms Nanthakumaran on the news.
Having left her Cardiff home at 03:00, she said waiting for days to pay her respects was “nothing to me”.
Decked out with a Welsh flag and chair, Anne has plenty of letters from the Queen and royal magazines to keep her company over the coming days.
As for food, she said she would be ordering a Deliveroo straight to her in the queue.
Security staff and stewards are lined up at regular intervals along the queue route, which stretches from Parliament’s tourist entrance at Cromwell Green down Millbank, past the Lords and Victoria Tower Gardens, across Lambeth Bridge and loops back north on the other side of the river past the Covid Memorial Wall.
Portaloos and crowd control infrastructure, such as barriers and temporary flooring, have been set up inside Victoria Tower Gardens, which is likely to be the peak of the queue before it leads into Cornwall Gardens.
