I can't even remember the name of the pub on Achill Island, in County Mayo, where I heard a phrase in Irish : 'Ronnoch mor' but I'm sure it was uttered by a big, red-faced, 60-ish commercial fisherman called Mangan. I asked him what it meant and he said, "The great mackerel".

Now at the time, which was the early '70's, Achill Island was one of the greatest sea angling spots in Ireland and Kevin Linnane, Des Brennan and I had been having great fishing there, drifting pirks with two mackerel baited hooks above them, getting triples, I kid you not, of big cod, pollack and red bream - though, quite often, the bream would be slammed by a tope on the way up.

So at first we didn't think of tuna. Mangan had put away a few pints - maybe, we thought, he was trying to kid us that there were 10lb mackerel out there off Achill Head.

But he wasn't, and when you look at the tail of a giant tuna and the blue-green sheen down its sides you'll see what Mangan was a getting at. It was bluefin tuna he was talking about, huge fish that the local fishermen feared because if they met one at best it would carry away their nets, at worst overturn their curragh, the frail, tarred canvas and wood canoes that a lot of them still fished from.

Bluefin tuna! Or tunny, as they used to be called off the Yorkshire coast in the '30's and '40's before the herring shoals that brought them within angling range were fished out, tuna of up to 800 lbs. The last one had been taken in, I believe, 1951. And that was the last seen of the species - the only big game saltwater fish ever to have been encountered around these islands.

Even if the big fish were out there off Mayo, though, we thought, we'd neither the tackle nor the boats nor, indeed, the knowhow to go after them. For the moment, it was just a dream.

Kevin, though, dreaming on, managed to take it a stage further. He was working for the Irish Inland Fisheries Trust (It later became the Central Fisheries Board) and somehow he managed to persuade his bosses to send him on a fact-finding mission to waters where commercial tuna fishing was going on - to the Bay of Biscay in fact. The tuna there were not the giant bluefins but the smaller yellowfin and albacore. Nevertheless he came back with a good idea of how to catch 'em.

At that stage, though, we were still thinking in terms of distance. The 'Ronnoch Mor' seemed to have been encountered inshore off Achill at one time, but there'd been no sightings for a very long while. We reckoned we'd need a big boat - a 60-footer maybe - to get out the 50 or more miles offshore where we thought the giant tuna might be.

So our quest was continually shoved onto the back burner as the 80's moved to the 90's. Meantime there'd been a lot of reports of small tuna species - mostly albacore - being taken off Kerry, but they weren't the one we were interested in. In '98, though, we thought we had a breakthrough when we were told - wrongly as it happened - that the Irish Ministry of Marine was going to make a big boat available to us, one big enough to sleep aboard and take us way out 80 miles or more to the Porcupine Bank where there'd been reports not only of giant tuna but of broadbill swordfish being taken by commercial longliners. But the boat we wanted didn't materialize.

For a few years, meantime, there'd been reports from the Donegal coast of bluefin tuna being taken in the nets of commercial 'tank boats' as locals called them. These were huge fishing craft capable of picking up a thousand tonnes of fish in a single haul . That was too big a load to be swung on board: instead a giant suction device emptied the net into a refrigerated tank. And with them had come bluefins of - we could hardly believe it - over 1000 lbs.

Once again we went looking for a boat. And this time we got lucky. Michael McVeigh had owned a highly successful taxi business in Belfast, but now - this was 1999 - a keen sea angler himself, he wanted a change of lifestyle. He'd built what he called an 'Anglers Village' on the Donegal coast at Downings and had ordered a new twin 300 hp 43 craft to take sea fisherman out to catch the usual cod, haddock and so on. Kevin got hold of him, though, and convinced to give giant tuna fishing a try.

At the time, the boat (later to be named the Rosguill after the rocky peninsula on which Downings stands) was only half built, but we thought we'd be in good shape for September 2000, prime time, so we believed, for hitting the bluefins.

But the best-laid planssuccessively, bad things began to happen. At the start of the year, Kevin was diagnosed with Motor Neurone disease, a muscle wasting affliction which would progressively worsen. Bravely, though, he decided to soldier on. Then I myself had a much lesser stroke of bad luck. In August I headed out to Malaysia to check out the black marlin fishing in the South China Sea and, trying to board a boat which I believed to have been securely tied up to the quay (it wasn't) fell and smashed up my left knee - which first put me into hospital and then sentenced me to a long spell on crutches. As Kevin was to say later, stick us both together and we just about added up to one whole angler.

And then, on top of that, as August slid into September, we got the news that the boat wouldn't be finished on time. Things looked black indeed for our bluefin tuna venture

Next week - What happened next