The coastal cliffs at this place are so intensely white that, with sunlight rebounding on three sides, the chalk face in Selwick’s Bay is almost blinding. It’s no more than 20m high here, but farther north at the RSPB’s Bempton reserve, with its breeding colony of 400,000 seabirds, the sheer rock rises five times higher.

It is difficult to process how a scene of such dramatic scale could be made by something so small, because, while there may be a touch of grandiloquence in their name – coccolithophores – it refers to algae. More than 100 million years ago these monocellular phytoplankton wafted in warm seas, and as they died they drizzled to the seafloor, adding their calcium-rich coccolith corpses to an immense, accumulating hoard. At Bempton’s sublime cliff-face, that collective graveyard is 100m deep – proof that the planet’s real magic can be assembled, had we but world enough and time, in the most mundane of ways.

At Selwick’s Bay, however, a momentary unfolding added to Flamborough’s all-encompassing story. House martins are known to nest below roof eaves and window ledges, but at one time they glued their mud cups to cliffs and sheer canyons. Here you can find the birds living in their original state, and one nest still held almost fully fledged young.

Through an entrance hole, I could just pick out four shining eyes and two wide-gaped mouths. They must have been a second brood, and the first-born siblings with their parents flickered in and out of that spot, or hovered before it like nectaring moths, pulsing on to the rock face an echoic shower of buzzy notes. All this seemed to say, “come out and join us”. The chicks wriggled and leaned out, yet for now they looked entombed.

But, then, the choice they face is to abandon everything they’ve known in their six-week existence, for all that they will become: gloom for sunlight, a mud-hole for an infinity of air, England for Africa, gravity for weightlessness, or, at least, a condition as close as is possible for any Earth-born vertebrate to enjoy.