Due to the wholesale elimination of London Underground staff and the closing of all the ticket offices, RMT (the Rail Maritime and Transport Workers Union) is striking against the London Underground. From late Saturday this weekend, all Sunday, and Monday.
The strike is by station staff.
The strike does not involve drivers so TfL (Transport for London - who are the employer) will try to run tube trains. The effect of the strike will be late opening, early closing, or complete failure to open some or many or most stations so the public will be unable to access any trains that may be running. It is unknown if drivers will have to pass any picket lines.
Buses and DLR are unaffected.