Thousands of eager shoppers in central London have been hit by delays following the start of a 24 hour tube strike.
Train drivers union Aslef called members out on strike following a dispute over demands for additional pay for working on a public holiday.
Football fans heading into London are also expected to be hit.
Arsenal have been forced to postpone their Premier League match against Wolves until tomorrow.
However, Chelsea will take on Fulham at Stamford Bridge later today.
“What we are asking for is a guaranteed level of service where people can be guaranteed at least every other year, every third year, a day off, and - for those who do come in - an incentive,” Aslef general secretary Mick Whelan told the BBC News Channel.
Whelan said the original dispute focused on “quality time off”.