Maintenance workers on the London Underground have voted in favour of strike action between 24-27 April.
The Rail, Maritime and Transport union, which represents around 1,000 tube staff, has said its members plan to walk out at 4pm on 24 April.
Piccadilly, Northern and Jubilee lines will be most seriously affected, although the workers also provide a number of services across the network, including emergency repairs.
Workers voted 4-1 in favour of the strike which demands that all tube workers are involved in the Transport for London pension scheme and receive equal travel concessions.
Distress over the planned strike has been expressed on Twitter, with many commuters seeing the action as a troubling sign just 100 days before the Olympics:
"So overground trains are messed up 72 hour tube strike announced Shite weather Good job we haven't got the Olympics this summer!!"
"ARGHHHHH at tube strike"
"I think cars in London just prefer to be stationary, it seems to be easier for them. May get the tube.oh hang on, they'll be on strike..."
"Last thing London businesses need is another Tube strike damaging the city’s reputation especially with just 100 days to go to Olympics"
"4 day tube strike next week. Brilliant! Thanks a lot Bob Crow you cretin!"