It may look like a place of worship in the summer – droves of Londoners desperate for a patch of grass under the leafy trees or a picnic spot overlooking the city.

But no one has been paying Primrose Hill spiritual heed for as long as the Druids.

To them the grassy knoll is seeped in far more than mottled sunlight – it’s a holy mound, appearing in ancient Celtic maps of the British Isles.

On Saturday (September 22), dozens of Druids, clad in long white robes and chanting mystical hymns, made their way up the hill to mark the autumn equinox, as they have been doing for 200 years.

The Druid order, which is an ancient pagan religion, follows the flow of the seasons, marking the changes at four sites across the UK.

One is the famous Stonehenge, which was ravaged by hippy festival-goers in the 1970s, but is back to its former heavenly state today – and is still emitting the positive energy which the Druids recognized back in the Iron Age.

Another is Primrose Hill.

Susan Winter, who took part in the ceremony on Saturday and has been a practising Druid for 30 years, explained the ancient significance of the green space.

“For hundreds of years, the Druids had to be secret,” said Susan, who lives in Beckenham, Kent, and is the director of a health and beauty shop.

“It would have been dangerous for them because it was prohibited at that time.

“But in 1717 a Druid priest announced they were finally going to have their first meeting in public, and it was on Primrose Hill.”

She added: “There is an ancient mound on Primrose Hill. It’s a Celtic site and if you look at maps of ancient mounds of the British Isles, it’s marked there.

“Some places people are just drawn to, not just because of the view. People sit down and want to spend time there. There’s something positive about the energy of the place.”

Susan said: “At Primrose Hill, the public have always been very respectful of what we’re doing.

“A lot of people sat down and listened when the chief gave his talk. It reminds people that it’s autumn and people seem to enjoy it – it marks the rhythm of life.”

A plaque atop the hill commemorates the Welsh Druid priest who first called the meeting in 1717 – and William Blake, who was part of the Druid order, has had his poetic words inscribed in stone on the hill.

Fans of pop group Blur have also flocked to Primrose Hill over the years to see graffiti lyrics “And The View’s So Nice” inscribed on one of its paths inspired by the band’s song For Tomorrow.

The lyrics were removed by Royal Parks, which manages Primrose Hill, earlier this year because they were classed as graffiti.

Blur fans campaigned for the landmark to be reinstated and the lines to be inscribed on the stone circle on the top of Primrose Hill, but Blake’s poetry was chosen instead.