Phoenix Natural Gas want to insert new gas pipes inside old ones located below the streets of Holywood in County Down.

These pipes used to transport gas between Belfast and the seaside town of Bangor a number of decades ago.

But the company are having great difficulty pinpointing exactly where the pipes are because old maps of the gas mains are either devoid of critical information or are missing.

Retracing old pipes

As a result, Phoenix engineers are planning to retrace the Holywood gas mains, armed with an old map and a secret weapon - the very last man to work for Belfast City Gas.

Frank McCoubrey: Memory tested

Former manager with Belfast Gas Frank McCoubrey, told the company there were two eight inch pipes running along the whole of high street in Holywood, to a depth of 24 to 28 inches.

"We would indicate areas approximately where the old gas mains were," he said.

"We'll probably have to take at least one, maybe two trial openings.

"But generally two openings are quite sufficient to pick up the mains."

As a result of his memory power, Phoenix have been able to keep their work to schedule, despite the missing information.

Dawson: Drawing on experience of former workers

Brian Dawson of Phoenix Natural Gas is delighted with Frank's brain power.

"If we can find the main line, that saves a lot of the cost and disruption and inconvenience to the public is minimised," he said.

"There are plans written in ink pen - some of them have been lost, so we're drawing on the experience of men like Frank and colleagues of his, to supplement that information.

"We found Frank to be very good. I would say about 90% of the information has been correct."

Frank is confident that his recollections of several decades ago are accurate.

"My only worries will be whenever they switch the live gas on and I'll not be there anyway," said Frank.

The new gas supply is already in use in properties outside Holywood and digging will recommence in the town after the summer break.