THIS episode opens with hundreds of thousands of turtles emerging from the ocean off the coast of Costa Rica so they can give birth. The camera pulls back and they seem like tiny specks on the sand, so vulnerable, and yet so sturdy, as they’ve been taking part in this ritual for thousands of years, unchanged and untroubled.

Then we see some “bachelor” sea lions who’re trying to pile on the weight and beef themselves up so they might attract a gal. Tuna is their favourite meal but the fish zoom around the waters at 40 mph, so a lovelorn sea lion has no way of catching one “but he has a plan”: they herd them like sheepdogs, trying to drive the tuna into a dead end where they’ll be trapped.

This week is about life on the coast, where the sea meets the land and “two worlds collide”. This brings “rock pool dramas” into the equation, and also sea birds. While sea lions might be chasing the fish, so are the hungry puffins, “the clowns of the sea”.

JULIE Walters “frolics” to Edinburgh this week, taking the coastal railway up from Newcastle.

She breaks her journey at Alnmouth to poke around the pretty seaside village before climbing aboard again on the way to Berwick Upon Tweed where she sits in the “cockpit” of the high-speed train. “Has Michael Portillo been on this train?” she asks the driver. “I just thought I could smell Lynx.”

We get a fine insight into a train driver’s life as he describes the risk of bird strikes, and his disdain for steam engines – which are just big kettles, he says.

After all the breeze and seaside it’s a relief when the train pulls into stern and imposing Edinburgh, and Julie checks into the very fancy Balmoral Hotel. But she doesn’t use the ordinary entrance which we plebs would utilise. Oh no, she’s whisked directly into the hotel from Waverley Station through a secret passage, once used by the rich and famous who didn’t want to mingle with the hoi polloi.

Behind a bland door lies a huge mahogany staircase which leads into a wide, white corridor along which the posh Victorian ladies in their crinolines would have flounced.