Last-ditch talks aimed at averting strikes by London Underground (LU) workers in a row over plans for an all-night Tube service will be held today.
Rail union leaders will meet LU managers under the chairmanship of the conciliation service Acas, with time running out on reaching a deal.
Members of three unions are due to stage two 24-hour walkouts from Tuesday and Thursday evenings which would cause travel chaos in the capital.
The drivers' union Aslef has said it will not join this week's strike after taking part in previous industrial action.
The unions are in dispute over pay and shifts for the new service, which is due to start at weekends from September 12.
LU has said it is operationally ready for the launch but unions believe it will be delayed because of the protracted row.
The executive of the Rail, Maritime and Transport union will meet after the Acas talks to decide whether to call off the strikes.
Unite and the Transport Salaried Staffs Association are also involved in the dispute.