The Northern Ireland Housing Executive had received consent to build a small estate in the Ferryquay Street area, overlooking the River Bann. Buildings still occupied the site, many of them derelict, but some still homes to Coleraine residents.

With buildings still standing, I was forced to find scarce areas of open ground where I might sink my trenches, and thus my small excavation crew and I knocked on doors, gained access to back gardens, opening trenches wherever there was an opportunity.

Today, of course, such matters are governed by government policy - Planning Policy Statement 6 - which requires developers to mitigate their impact by funding excavations where archaeological remains will be destroyed by development.

In those days, however, government archaeologists such as myself worked within a limited budget for excavation. Margaret Thatcher's election, and a short-term embargo by her on expenditure and "working away from home" expense accounts, meant that I spent many uncomfortable nights sleeping in my car, rather than enjoying a B&B!

By now, I had begun to immerse myself in Coleraine's history, being fortunate to have an invaluable primer in the Reverend T H Mullin's 'Coleraine In Bygone Centuries', published in 1976.

I still own the paperback version, albeit its spine is cracked and the pages loose. Anyway, foraging around the Ferryquay Street area, we found various patches of open ground, where no-one objected to archaeologists digging holes. And so we began….

Amazingly, we immediately (and luckily) lit upon the remains of a massive mortared stone wall, which had clearly been built to a thickness of six feet (photo 1).

No-one builds a wall that thick for domestic purposes. Hence, the presumption was that it was military. Enough of it was revealed to indicate its course, and a second trench, in a nearby garden, found it again.

This time, however, rather than a stretch of wall, we uncovered a block of masonry which was clearly a corner (photo 2).

But this wasn't a right-angled corner – rather, it was acutely angled. Any student of military buildings in the 17th century (and we had dating information from the pottery finds which accompanied the discovery) knows that such an angled corner presumes either that the original structure was either triangular, or that we were looking at a 'bastion' (a spear-shaped projection on which was mounted small-scale artillery – reaching out from the corner of a fort to provide a 'killing ground' of projectile fire).

That was it.

We didn't have the space or opportunity to 'join the dots' any further. Rather, we had to settle for two sightings of what was clearly a massive stone and probably military fortification. Back to Mullin's book, and the trail towards the evidence of an episode in Coleraine's history.

Three starting points – a 1738 map, stored in the Public Record Office, shows a plot of land in this area, identified as 'formerly the citadel'.