Britain’s narrow seas and sluicing tides have always challenged ships; never more than today, as the vessels grow more unwieldy. Yet the pilots who safely bring them in and out go largely unsung. The grounding of the outbound container ship Cortesia yesterday, mere hours after dropping her Thames pilot, brought home yet again the skills and dangers. For me, it added an edge to a journey through the pilots’ world that I began, many months ago, for Radio 4.

Our story came to a head in the bleak magnificence of Teesside. Here blast furnaces tower, vast steam clouds whiten a slatey sky; and through the heart of it glide the tankers, heading upriver to collect the fruits of the Ekofisk field. Geoff Taylor, retired maritime pilot, is immensely happy to show it all to us. He loves the Tees, every treacherous foot of it. “This is the lifeblood of Britain!” he cries, gunning his big car down a long, weird peninsula of reclaimed slag. “Oil, chemicals, iron ore for the steelworks – moving in and out, day by day and night by night. . . 50 million tonnes a year . . .”

I am in the car with Simon Elmes, veteran Radio 4 producer and creative director, and Geoff is thoroughly enjoying our slack-jawed southern wonder. Teesside has felt the familiar processes of British manufacturing decline – industries closing to be replaced by heritage museums and bird sanctuaries – but what remains is all the more striking. And the port operation is the most striking of all, because when it comes to shipping movements the heavy trades still flourish. Well, they have to: nearly everything we use and much of what we eat comes by sea, in vast ships like lateral skyscrapers; our few solid exports go out the same way. Teesport is one of our major ports, and the one Geoff loves best, because here he practised as a maritime pilot. Which is why he has brought us here on a violent winter’s day, to a bleak, brick shack on the reclaimed peninsula. This is the headquarters of Tees Bay Pilots, whose job is to guide the ships in.

From the upper room we can see the nature of their task. Over to the right, two big ships pitch violently a mile or so off the bone-white beach. On the left the Tees sweeps in, an onshore gale throwing curving white surf halfway up to the port, pressing sideways on exposed acres of steel as a third vessel struggles with her tugs. A new call crackles on the radio, to be met with a brisk “Have you got the draft, please?”

The programme Simon and I are making began 250 miles south of this bleak spot, in the cosy surroundings of a lunch on HQS Wellington by the Thames Embankment, where I found myself sitting with Geoff Taylor, then president of IMPA, the International Maritime Pilots’ Association, and his world colleagues. One was discussing Rio, others telling tales of the Yangtze or the Baltic. I was entranced: I had never thought much about the pilots who guide these vast modern ships safely from the open sea to each crowded port. “Nobody does,” says Geoff. Even yachtsmen like me tend to have vague retro ideas about the bold old sailing-cutters racing out to Land’s End to fight for trade, or the smiling Dutchman in his blue cap helping the yacht into Flushing in Arthur Ransome’s We Didn’t Mean to Go to Sea. Now a new picture unfolded, of an ancient trade mutating quietly into a high-tech age.

The pilot is the human link between the immemorial isolation of the seafarer and the bustle of the port town. Or rather, these days, the container or tanker terminal behind its razor wire.

They began to tell me how it is to head out into the open sea in a small boat, to board a strange ship and meet captains under commercial stress, worried about time slots, surrounded by lonely Third World crewmen. The pilot must assess the ship’s handling, the weather and all he knows about the river. There is little margin for error: tens of thousands of tonnes of steel must be floated to its berth with as little as 90cm clear water under the keel. I quoted this figure to a Rotterdam pilot, who laughed and said: “We go to 30cm.” Less than a page of this newspaper.

The human aspect of the job fascinated me. “I know what I’m getting into, from the first rung of the ladder and the angle of the captain’s head,” says Geoff. “I’m a psychologist, have to be. You get a sense of the ship – is it well run, is it happy, is it tense, how has it been for that month at sea? Is the master assertive or co-operative?” “Or bonkers,” says a Thames pilot. “A bad ship, you feel the rust on the ladder, you look up at the scruffy individual at the top who looks as if he’d like to stick a knife in you . . .” “You smell it,” says another. “That old-ship smell of the toilets or the galley . . . you think, maybe I won’t eat on this one. But when the sugar ships come up the Thames to Tate & Lyle, Silvertown, you get this lovely strong molasses smell.”

They mainly speak with fondness of the ships. “Well, it’s the most ancient of human experiences, transition, entering or leaving a harbour,” says Geoff. “You are going out, perhaps on a wild night, to guide a stranger into the safety of your port, bringing them to your country after weeks at sea.”

The captain remains master, but it is the pilot who designs the dog-leg course to safety, preventing the ship running aground, obstructing the port or smashing up the dock. Standing alongside the captain, “feeling the vibes”, observing tactful etiquette, he makes snap judgments. How fast do the engines respond? Must he deliberately break the harbour speed limit to keep under reasonable control? The captain may disagree, but the pilot knows the sharp bend coming, the awkward tide.

“There can be tension . . .” says Geoff. Or, indeed, too much agreement. Two Thames pilots laughed about a well-known figure called “Captain OK”, whose grasp of English is weak but who takes Asiatic politeness to extremes. “I say half-speed ahead – he says OK. Nothing happens. I say it again, he says OK . . . Still nothing . . .” “I’ve known some,” says a colleague, “where you ask for Slow Ahead and the engine-telegraph handle comes off in the captain’s hand, and nobody seems to know what to do about it.”

The internationalism of the pilots runs alongside a private passion for their own rivers. They all have masters’ tickets and deep-sea experience, but deeper still is their intimacy with their own waters. John Clandillon Baker and Howell Jones Pugh spread out their Thames chart in front of me. “See – now there, above Gravesend, the tide goes round in a circle and a big ship can be swung right round – Broad Ness is tricky, someone in their wisdom has stuck a couple of oil jetties there – Stone Ness is OK . . .”

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