The route for Sunday's March for England has been slightly altered following the collapse of a road.
Nationalists will now be directed to gather at the bottom of Middle Street in Brighton – rather than West Street as originally planned.
It follows the part collapse of the A259 King’s Road this morning (April 25).
Workmen had been fixing a fire exit at the Fortune of War pub, situated below the road.
Superintendent Steve Whitton said: "We have been working with the council and their engineers to assess the structure of the road and have decided to move the start of the march further eastwards on the A259.
"The march will now start at the A259 junction with Middle Street. They will then march east to the junction of Pool Valley and back again. It will still start no earlier than 12.30pm and finish no later than 1.30pm.
"Our focus is, as always, keeping people safe and we have worked with the council to make sure people taking part in both the march and the counter protest, as well as visitors to the city, are kept safe. For this reason the eastbound carriageway will be completely closed at West Street.
"It is really important people understand that the carriageway is closed for safety reasons and they should not enter the area which is cordoned off under any circumstances.
"Please talk to our officers, who will be very visible in the city, if you have any concerns."
Geoff Raw, from Brighton and Hove City Council, added; "Structural engineers will be working over the weekend to assess the extent of the problem and which seems to have been caused by historic alterations to premises in the arches.
“We're working as swiftly as possible with the police and key partners to ensure public safety and to keep the traffic moving as smoothly as possible.
“A contra flow system is now in place between Middle Street and West Street, please allow extra time for journeys through this area and check the council website for updates."