Many London subway drivers staged a one-day strike Monday, creating travel headaches for thousands of shoppers trying to take advantage of Boxing Day sales in the British capital.
A notice posted on the London Underground website told travellers on the Tube to brace for "significant disruption."
Most subway lines were partially closed and customers faced severe delays. London Underground vowed to "keep London moving" despite a "completely unnecessary strike action."
As of mid-afternoon local time, most subway lines were offering reduced service and all of London's bus routes were in operation. Extra buses were being put into service in London's main shopping areas. Some stations were closed.
"We are operating a service on most Tube lines, including key lines serving the West End, supported by London's 700 bus routes and extra buses," said London Underground's chief operating officer, Howard Collins.
The strike was called by the ASLEF union to demand extra pay and a day off for members working on the Boxing Day holiday.
Despite the disruptions, large crowds of shoppers jammed the big department stores. Department store chain Selfridges said its first hour of business Monday was its biggest ever.