Ten of thousands of people have been disappointed trying to get tickets for an audience with Michelle Obama at London's Royal Festival Hall.
Many on social media have said there were more than 40,000 people in the tickets queue.
The former US First Lady is appearing at the 2,900-seat venue on 3 December.
Tickets are appearing on Viagogo for thousands of pounds, but the venue said it has asked for them to be removed.
I was #30562 in the queue....so close https://t.co/5araYLvTZK— nick grimshaw (@grimmers) November 8, 2018
There are 4413 people ahead of me in the queue for michelle Obama tix at the south bank. *laughs for all eternity the cries for whatever time is left*— morgan lloyd malcolm (@mogster) November 8, 2018
Any tickets bought from unauthorised third parties will not be admissable, the venue said.
We have asked Viagogo to remove the tickets available on their site. Tickets bought from unauthorised third parties will be cancelled and invalid for entry. 1/2— Southbank Centre (@southbankcentre) November 8, 2018
They will talk about her experiences from childhood, her work, motherhood and "her time spent at the world's most famous address".
She will also share "life lessons learned" while hoping to "inspire people to become the very best version of themselves".
People tweeted that they had been queuing since 4am at the venue.
The South Bank Centre, which is a multi-arts venue next to the River Thames, tweeted at 10:30GMT to say they had sold out.
People were queuing at 4am for Michelle Obama’s presale tickets. If you are serious about going you need to be up early!!! Don’t log on at 8am, don’t get to south bank centre at 9am you won’t stand a chance— Abigail Kwakye (@Abigail_Kwakye) November 7, 2018
The London date is in the middle of a 13 night tour starting on 13 November in the Obama's hometown of Chicago, where she will be in conversation with Oprah Winfrey.
Tickets sold fast in the US and Obama tweeted she was "truly humbled by the response to my upcoming book tour".
The South Bank Centre said they are also in the process of identifying touted tickets.
They told the BBC that due to "extreme demand for this event, unfortunately there will be people who are disappointed".
Truly humbled by the response to my upcoming book tour. I can’t wait to share BECOMING with all of you & hope to see you somewhere along the way! pic.twitter.com/uT7im9hnFk— Michelle Obama (@MichelleObama) September 20, 2018
But they added they had "worked hard to ensure that tickets are available to as wide an audience as possible, by limiting tickets to two per booker and ensuring there is a lower price point of £30."
Three hundred tickets have been held back to be given free to secondary school pupils in London and the UK, as well as local charities.
The South Bank Centre said they do not have exact figures for how many tried to get tickets.
A proportion of tickets went on sale yesterday for the venue's members, with the rest going on sale to the general public at 10am today.