Even in midsummer, the ancient hazelwoods on the Hebridean island of Seil are cool and quiet. Countless slanted stems of hazel support a thick canopy, which blots out the sun and blankets everything below in a sort of “fairytale darkness”, says Bethan Manley, a biologist at the Wellcome Sanger Institute.

Moss and lichen coat branches threaded with honeysuckle, forming a great dome above you, adds David Satori, a researcher at Royal Botanic Gardens, Kew.

This rich forest, on Scotland’s Hebridean islands, is a remnant of one of Britain’s oldest woodland environments. When the last ice age ended, the mile-thick glacier that had buried northern Europe melted away and hazelnuts sprouted across the rock left behind.

Scientists can date when those forests sprang up across the west coast of Britain and Ireland, says Satori, because “about 10,000 years ago, you have a massive spike in hazel pollen”. Scottish lichenologists have estimated these particular woodlands might have been around since 7,500BC.