A little over two hours ago tube maintenance workers walked out, starting a 3 day strike over pensions and benefits.
The question is, will anyone notice?
The RMT says service will be affected. TFL says there won't be a major impact.
Our business correspondent, Glen Goodman, spoke to Jon Lamonte from Transport for London, and sent this report from RMT Headquarters.
Maintenance staff on three tube lines are entering their third day of strikes today.
A strike affecting the Jubilee, Northern and Piccadilly lines goes ahead from 4pm.
Union bosses have forecast "widespread" disruption, as workers who maintain and upgrade tube lines go on strike next week.