Travellers are leaving East Brighton Park where air ambulances land when they bring patients to Accident and Emergency (A&E) at the Royal Sussex County Hospital.
They were ordered off the land after twice being asked to make space for helicopters to land this afternoon (Wednesday 9 April).
One of the patients was a 69-year-old woman who was thrown from her horse in High Hurstwood, between Uckfield and Crowborough, at about noon.
She reached the Royal Sussex by 1pm after the Kent, Surrey and Sussex Air Ambulance was called into action.
Sussex Police said: “Police were informed of travellers at East Brighton Park, off Wilson Avenue, Brighton, on Wednesday (9 April) at around midday.
“Two helicopters needed to land at the park for medical emergencies and the travellers moved immediately to allow them to land.
“They have now been served with a notice under section 61 of the Public Order Act requiring the travellers to leave.
“They are now in the process of leaving.”
Brighton and Hove City Council issued a statement earlier about an “unauthorised encampment of travellers at East Brighton Park”.
It said: “We have visited this site with the police and we are currently undertaking a community impact assessment to determine the most appropriate course of action.”
The council also issued an update about the unauthorised encampment of travellers at Stanmer Park, saying: “An eviction was due to take place on Wednesday 9 April. The group left the site voluntarily.”
There is still an unauthorised camp on land off Lynchet Close in Hollingdean.
The council said: “A group of travellers remain encamped on land adjacent to Lynchet Close.
“We have visited this site with the police.
“A possession hearing for this land will take place in the county court on Tuesday 22 April.
“Once we have obtained a possession order, we will carry out an eviction as soon as is practicable.”