The project to upgrade the historic site, will be let as a two-phase job worth up to £35m.

The revamp aims to boost visitor facilities while also protecting and restoring the Observatory’s listed buildings.

Phase one is due to start in early 2026, covering the southern end of the site. The northern section will stay open until late 2026 before closing for phase two works in early 2027.

New-build elements include a modern entrance pavilion, a garden walkway, a new stair up to the Great Equatorial Building, a café kiosk, and a science engagement space connecting the South Building and Planetarium.

A site-wide heat pump system will replace gas infrastructure, and services will be upgraded throughout.

Conservation work will tackle windows, roofs, and building façades to restore the historic fabric. Lift installations and landscaping upgrades will also improve step-free access across the sloping site.

Firms have until 5 September to express interest, with the award expected by the end of October. Construction will run from January 2026 to February 2028.

Full details on the Delta eSourcing portal here.