The 300 staff employed by outsourcing giant ISS work as porters, caterers and cleaners at five hospital sites - Croydon Hospital, Maudsley Hospital, Lambeth Hospital, Bethlem Hospital and Ladywell Unit, Lewisham - are in dispute with the company over pay, terms and conditions.

The workers have been on strike from 29 November and have staged picket lines outside their normal places of work.

A spokesperson for South London and Maudsley NHS Foundation Trust previously said: 'Our staff are our greatest asset, and we know that staff who feel supported at work provide the best care for our patients and the people who use our services.

‘We want our staff to be able to support themselves and their families and afford the costs of living in London.'