Actress Penelope Keith is backing a campaign against NHS cuts in Surrey.
Penelope Keith is backing the campaign in Godalming
The Good Life star will board a bus to publicise longer travel times which could result from reforms at Guildford's hospital, campaigners said.
The Royal Surrey is one of several hospitals in Surrey and Sussex where services are currently under review.
South East Coast Strategic Health Authority has said no decisions have yet been made under the Fit for the Future NHS review.
Ms Keith was setting off on her bus journey from Godalming on Tuesday.
She was being joined by politicians, residents and campaigners.
Owen Bethell, from Save the Royal Surrey Campaign, said: "Some of the more deprived and remote areas in Surrey are likely to suffer disproportionately from any relocation of services."
Primary care trusts across Surrey and Sussex are expected to publish formal proposals for hospitals in the next few weeks.
A three-month public consultation will then take place.
Surrey Primary Care Trust has said it hopes to retain services at all three of its sites - Ashford and St Peter's, Frimley Park and the Royal Surrey.
This month David Cameron met nurses and patients at the hospital's accident and emergency department which campaigners fear could close.
Ms Keith, from Milford, was made a CBE in the new year, for charitable services. She was high sheriff of Surrey in 2002 - the third woman to hold the post.