London's cabbies are blocking off access to the Shard, in protest at the lack of a suitable taxi rank.
Drivers are there to mark the opening of a new hotel - the Shangri-La - at the building.
Unite's cab section has said that the demonstration is in response to Transport for London's refusal to erect a taxi rank near the building's entrance on St Thomas Street.
TfL has expressed disappointment at the demonstration, signalling that such action "will only disrupt the travelling public, the very people that the taxi trade are supposed to serve."
Garrett Emmerson, TfL's chief operating officer for surface transport, said on the issue of a taxi rank that TfL has "recently reached an agreement with the owners of The Shard that will enable a single taxi to rank directly outside the building."
Taxi drivers protest at the Shard https://t.co/nTtaTxeLjB— London SE1 (@se1) May 6, 2014
Club banner at London bridge. pic.twitter.com/4WjhSz9TyV— The LCDC (@The_LCDC) May 6, 2014
Clean cab and heading to the shard pic.twitter.com/hEldmMIC5O— alistair greecy (@alistairgreecy) May 6, 2014