The GMB union says it expects between five and ten thousand people to join a march through west London today in protest against the closure of emergency departments at several hospitals.
Plans have been outlined for the closure of facilities at Charing Cross and Hammersmith & Fulham Hospitals, and Ealing and Central Middlesex Hospitals.
The Union says the closures would lead to longer waiting times at other hospitals.
A spokesperson for NHS North west London said the plan was currently being consulted upon, and they would like to hear people's views.
The march will start in Shepherd's Bush at midday.
More top news
A drunk man who narrowly escaped death when he lay down between train tracks in Harlow has been given a 12-month community order.
A man from north London has been charged with the manslaughter of Louella Eve Fletcher-Michie, who died at the Bestival music festival.
The mother of Ellie Butler - the six-year-old murdered by her father - has lost a bid to challenge her conviction.