Olympian Barbara Kendall has slammed Heathrow airport, describing it as a "nightmare."
Kendall, an IOC member, arrived in London three days ago.
She took to Twitter to vent her frustration, tweeting, "Heathrow Airport Immigration is a nightmare!! took me 2 hours to get through and it is not Olympic timeyet."
The five-time Olympian is in London ahead of the Olympics, which begin on July 27.
Another notable tweet from @disabilityaid said, "went through terminal 5 Heathrow Airport on Sunday - a nightmare! 4 hour delay at immigration. Avoid Heathrow at all costs!"
Kendall has since tweeted complimentary comments about London's fine weather and her excitement at the Olympics sailing venue.
London Mayor Boris Johnson wrote to Home Secretary Theresa May last month to express his "serious concern" about immigration problems at Heathrow.
He said the difficulties at Heathrow gave "a terrible impression of the UK" and it was unfortunate that the country's main port of entry was "gaining such a poor reputation".