What’s set to be the biggest strike since the 1979 Winter of Discontent is taking place today – but what services have been affected?
Early government figures suggest that almost three in four schools are being hit, although that number could rise.
The Department for Education (DfE) believes that more than half of England’s 21,700 state schools (58%) are closed, with a further 13% partially shut.
Headteachers, teachers and classroom assistants from all the education unions are taking part in the action.
In England, 40,000 outpatient appointments are being rescheduled, 500 non-urgent operations postponed and 12,000 patients will have diagnostic tests rearranged.
This estimate is based on 20% of the workforce taking part, including nurses and radiographers.
In Scotland, more than 3,000 operations and appointments will not go ahead.
Emergency services and operations are expected to continue as normal.
Heathrow Airport has warned passengers face 12-hour queues if, as predicted, 18,000 border staff join the walk-out.
Civil servants have been asked to step in and embassy staff may be flown in from abroad to help man immigration booths.
British Airways has offered its customers the chance to switch their flight to a different day.
In Northern Ireland, the industrial action means the public transport network will be shut down.
In the north of England, the Tyne and Wear Metro will be affected but other networks, including London transport, should run as normal.
LOCAL AND NATIONAL GOVERNMENT
Bin collections, street cleaning and council-run leisure centres are affected.
With traffic wardens joining the strike, parking tickets may not be issued – but only in some areas.
Jobcentres are shut, Whitehall departments will operate with reduced staffing levels and MPs will find their staff canteen closed.
Cases may be postponed and courthouses closed for the day. Any one expecting to take part in a court case would be advised to check locally.
Tests have been cancelled as examiners are among those joining the action over pension reforms.
Union rallies are being held across England, Wales and Scotland. Details of which areas will be affected can be found on the False Economy website.