Tickets to see Michelle Obama speak in London have been offered for re-sale online for hundreds of times their face value after rapidly selling out.
The former First Lady is due to appear at London's Southbank Centre on December 3 to talk about her upcoming book 'Becoming'.
The venue's capacity is just over 2,700, but such was the demand for tickets that more than 55,000 people were in an online queue at one point.
Unsurprisingly tickets soon sold out after going on general sale on Thursday morning, but some have been listed on resale site Viagogo.
Official prices for the event varied from £30 to £125, but there were tickets on sale on Viagogo for thousands of pounds, with reports some had been offered for more than £70,000.
The Southbank Centre said any tickets being sold "without our authorisation by any unauthorised third parties" will be cancelled.
"We are aware that a small number of tickets to this event have appeared on third party resale sites," the centre said in a statement. "We take secondary ticketing very seriously and aim to discourage this by stipulating that tickets should not be resold for profit or commercial gain.
"If we find tickets on sale without our authorisation by any unauthorised third parties they are identified and cancelled.
"We are in the process of identifying touted tickets and we have contacted third person resale sites and asked them to remove the tickets as resale is against our terms and conditions.
"Tickets will only be available to collect on the night and ticket holders for this event will be required to bring a form of identification."
Southbank Centre members were able to apply for pairs of tickets on Wednesday, with a further allocation then going on general sale on Thursday.
Many who had logged online in an effort to get tickets shared their struggle to get to the front of the queue.
The event will see Mrs Obama discuss her memoir with novelist Chimamanda Ngozi Adichie.
All those attending will receive a hardback copy of 'Becoming'.
The centre is donating 300 free tickets to secondary schools across the UK, as well as some local charities.