More strikes by Tube workers
Staff are set to walk out at the end of the month.
More London Underground workers are to strike in a worsening dispute over jobs and pensions.
Unite said hundreds of its members in engineering, maintenance and management roles will walk out on July 26 and 28.
Members of the drivers' union Aslef and the Rail, Maritime and Transport union on the Tube are also taking industrial action later this month.
Unite is calling for guarantees that there will be no increases in employee contributions to the pension scheme, no decrease in employer contributions, and no reduction in pension fund benefits.
The union is also calling for a guarantee of no job losses in London Underground following Government funding cuts.
Unite general secretary Sharon Graham said: "Unite members on the London Underground will not accept attacks on their pensions and jobs.
"The workers are rightly demanding copper bottomed guarantees from Transport for London.
"Without these solid guarantees strike action will continue and the workers have Unite's complete support."