In 2018 Pritchard Architecture won a competitive tender to complete a feasibility study for Hilsea Lines, a Scheduled Ancient Monument in Portsmouth. The feasibility study included a full condition survey, mothballing strategy and options for future development.

The Hilsea Lines were constructed between 1858 and 1871 and included special fortified bridges for road and rail access. Even before their completion the Hilsea Lines had been rendered obsolete by the 1859 Royal Commission and advances in artillery technology. The development of rifled artillery meant that it was now possible for an enemy to occupy the high ridge of Portsdown Hill north of Portsmouth and shell the naval base from several miles away without having to attack the Hilsea Lines. To counter the new threat a series of “Palmerston Forts” were constructed on Portsdown Hill and the Hilsea Lines were scaled back. In particular a pair of forts that it had been planned to place behind the lines were not constructed.

‘Bastion 5’ is the eastern casemate range to the centre bastion. These casemates, and their related gun gallery are the most physically isolated elements of the lines. They are derelict and subject to ongoing vandalism possibly associated with drug use. The east centre curtain is punctuated by what is possibly the shortest railway tunnel in Britain, where the Portsmouth - London mainline leaves the island.

Portsmouth City Council worked in partnership with Historic England to fund a condition survey and develop a mothballing strategy for a section of Hilsea Lines.

The overall purpose was to assess the condition of a defined section of Hilsea Lines and from the assessment produce a ‘mothballing’ strategy for the eastern part of the centre curtain, also known as Bastion 5. It is intended that the strategy will reduce risk to the site to such an extent that it can be removed from the Heritage at Risk Register.

Project Details

  • Client: Portsmouth City Council/Historic England

  • Designation: Scheduled Ancient Monument

  • Status: Completed December 2018

  • QS: Michael Edwards Consultants Limited

  • Structural Engineer: Marbas

Clare Dawe