Millions of commuters cycled, trudged and waited in snaking bus queues on Monday as a strike by London Underground station staff shut down much of the city's subway network through to Tuesday morning.

There was a 149 per cent increase in Santander cycle hires while commuters opting for buses have complained of overcrowding.

"It is really scary out there, cyclists are taking huge chances," doctor Simon Quantrill said. "The traffic is mad."