Dates have been agreed for the final phase of a National Trust sewage project road closure.

Phase two to connect Uppark House and Garden to the mains sewage system at South Harting will begin on March 31.

The work will require the closure of a short section of road between the B2146/B2141 junction and Uppark.

It will run for five to six weeks and will be completed between May 4th and 11th, including an extra week built in to account for unavoidable delays.

The second phase is the final stage of the project, following the completion of phase one towards the end of October 2024.

The timings of the work were agreed in consultation with representatives of Harting and Compton Parish Councils and local councillors, schools, businesses and farmers.

Dates including school holidays were chosen in order to reduce disruption for pupils and parents travelling to and from school. The work has also been scheduled to avoid peak summer trading periods for local businesses and harvest time for farmers.

Gordon Gardner, Uppark House and Garden general manager, said: “We’re pleased to have agreed dates for the work that take into account the needs and interests of as many different members of the community as possible.

“I know road closures will always cause some inconvenience, but we’ve worked with West Sussex County Council and our contractors to ensure the project is completed as quickly and efficiently as possible. We appreciate people’s understanding as we carry out the work.”

During the road closures, signs will be in place notifying motorists of alternative routes.

Traffic south of the site travelling to South Harting will be diverted south along the B2146 towards Chichester then north along the B2141.

Traffic going south from South Harting will be diverted along the B2141 to Chichester where vehicles travelling towards Compton can head north on the B2146.

Stagecoach’s 54 bus service will also follow alternative routes between South Harting and Compton, using the B2141 and Long Lane instead of the B2146 - the operator will place temporary bus stops along the diversion.

The project involves a road closure rather than temporary traffic lights because some sections of road do not have the minimum width required to safely accommodate a traffic lights system.

Although the closed section of road crosses the South Downs Way walking trail, people will continue to have access to the trial. During phase one, some motorists used the South Downs Way as a detour. Mr Gardner said similar attempts during phase two would be treated very seriously.

He added: “Attempting to drive a vehicle down a track designed for walkers and cyclists is not only dangerous, it’s also illegal.

“Unauthorised drivers who try to use the South Downs Way will be liable for prosecution. While the work is taking place we will use extra signage to warn drivers against this and will consider options to prevent cars from accessing the track.

“Anyone thinking of taking a vehicle along this part of the South Downs Way should also be aware that it crosses the closed section of road, so there will be nowhere for them to go anyway.”

Steps will also be taken to prevent a repeat of the break-ins and vandalism to the works site and machinery during phase one of the project, which caused several days’ delay to the work.

During phase two, contractors will use CCTV and automatic numberplate recognition technology to help secure the site. Any unauthorised site access will be reported to the police

The work at Uppark marks the first time the 17th-century house has been connected to the mains sewage system. This sustainable solution will avoid unnecessary future disturbance within the South Downs National Park and will bring the system in line with Environment Agency regulations.

The new system has been designed to empty into the mains at South Harting during off-peak hours only.

Uppark House and Garden is currently closed to visitors while this work and a number of other essential renovations are carried out. It is due to reopen in summer this year.