The workers, in the RMT union, were beginning a 48-hour strike over pay.
They work for an agency, Initial, which is contracted to Network Rail. The cleaners maintain the station facilities, including the Eurostar first class lounge.
They are demanding a pay rise to lift them up from their current poverty wages. Bosses have offered workers £6.76 an hour, a 13p an hour rise on their current wages.
The RMT is demanding they get the London Living Wage of £8.30.
The RMT’s assistant general secretary Pat Sikorski was on the picket line.
He told Socialist Worker that the dispute was a “microcosm” of widening class divides in London.
“We want to spotlight Network Rail’s role in this,” he said. “They can afford to offer massive bonuses for their top directors.”
Sikorski added that Network Rail should step in and pay more for their cleaning contracts if that would ensure decent pay for cleaners.
Initial have refused arbitration and are using a scab agency to try and break the strike. Cleaners plan another 48-hour strike on 1 March.
This is the latest in a series of disputes where RMT cleaners have demanded better pay—and won.
Cleaners employed by OCS on the Eurostar recently won a pay rise from £7.40 an hour to £8 by November.
And cleaners on the West Coast main line struck last year to win a 10 percent pay rise.