Commuters are facing the prospect of more Underground strikes as union leaders step up their campaign to halt the Night Tube.
A mass walkout by workers tomorrow evening is expected to paralyse the Underground system for more than 24 hours.
Union officials are expected to meet next week to plan further stoppages if talks fail to resolve the dispute.
A 48-hour shutdown or two 24-hour strikes in the same week are believed to be under consideration.
'All options are under discussion', said one source.