It’s been described as the ‘Sistine Chapel of the UK’ by experts – and this month visitors will have the chance to get closer than ever before to the ceilings of Greenwich’s Painted Hall.

Artist Sir James Thornhill spent nearly 20 years creating the Baroque frescoes that cover the ceiling and walls of the room inside the Old Royal Naval College – built by Sir Christopher Wren between 1696 and 1712 – which depict some of Britain’s greatest maritime triumphs.

Covering 40,000 sq ft, the painted surfaces date to 1706 and are undergoing a two-year-long restoration to bring back their original 18th-century vibrancy. London practice Hugh Broughton Architects has also been enlisted create a new visitor centre, Sackler Gallery and café as part of the £8.5m project.

‘The Painted Hall is one of Britain’s greatest architectural and artistic treasures, and this project aims to raise it to the national and international prominence it deserves,’ says William Palin, conservation director.

Beginning 1 April, visitors can book daily ceiling tours of the great room and see the conservationist work up close on Thornhill’s masterpiece.

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