As letters go, it was short and to the point. Several months ago, businessman Harry Crosbie wrote to this newspaper, wishing a “happy 300th birthday” to Dublin’s Great South Wall.

“On a recent walk my friend and I commented on how the granite blocks had moved and settled and become uneven over the centuries,” he wrote. “This makes walking difficult, and means that elderly and disabled people cannot enjoy this unique and wonderful experience.”

In the letter he proposed a “simple and inexpensive solution” that would improve the walk, as “you would not need to be looking down all the time”.

Crosbie says the phone didn’t stop ringing afterwards with messages of support, and he credits his friend – a “well-known cranky 81-year-old who used to live in Howth” – with putting him up to it in the first place. That 81-year-old would be Gay Byrne. “We meet up and walk the South Wall regularly,” says Crosbie. “And we had been talking about a friend who’d fallen there and broken her nose.”

Byrne laid down a gauntlet, Crosbie recalls: "Something like, 'Okay, smart arse, how about you do it. You're good at getting big projects off the ground'. "

Those big projects have included the building of the Point music venue, now the 3 Arena, back in 1988, and the Grand Canal Theatre (now the Bord Gáis Energy Theatre), designed by Daniel Libeskind, which have generated employment for hundreds and revenues of millions of euro for the capital.

This time last year Crosbie was locked in court combat with Nama. He also backed an unsuccessful public appeal to halt the sale of the theatre.

Now the businessman has a spring in his step as he recalls days spent angling off the South Wall, at a time when his father, Henry, was running a haulage business close to the North Wall.

The longest breakwater

The Great South Wall was the longest breakwater in the world at the time of its construction, which started in 1716. The first thick oak piles driven in earned it the nickname “The Piles” among the public at the time. Dublin Bay had been a hazardous approach for shipping due to a series of sandbars, and many craft foundered while trying to navigate across to the river Liffey mouth during stormy weather, resulting in many deaths.

The piles were anchored by baskets of gravel, and a stone wall linking them to the quays was built in 1756. Large granite blocks from Dalkey quarry – similar to those used much later for the Dún Laoghaire piers – were shipped over in barges to strengthen the structure. During those years, there was yet another dramatic reminder of the bay’s dangers one October night in the late 1760s, when two ships were unable to cross the Liffey bar and foundered off Ringsend.

Rachel and Mary Pidgeon – daughters of the then recently deceased John Pidgeon, who had been watchman at the South Wall – took to a small boat and rowed across, saving one man and his child from the wrecks. As late maritime historian Dr John de Courcy Ireland recorded, the rescued man was a Philadelphian, and a widower, who was so grateful that he promptly proposed to Mary Pidgeon and took her and her sister home to Pennsylvania.

The wall was finished by 1795. It was 32ft thick at the base and 28ft at the top. Poolbeg lighthouse, which had already been built in 1768, was laid on a foundation of masonry at its head. The lighthouse ran initially on candle power, before switching to oil in 1786, and was painted red to signify a port side navigational mark for ships. Its green or starboard mark, the North Bull lighthouse, was built after 1816, when the North Bull Wall was built on the advice of Capt William Bligh.

Bligh, better known for his HMS Bounty experience than for his survey of Dublin Bay, recommended in 1803 that a matching breakwater should be built parallel to the South Wall. He predicted – correctly – that it would create a scouring action that would deepen the river Liffey channel. Dublin Corporation amended his plan to build it southeast of Clontarf, and it was finished in 1842. The sand that accumulated alongside it created Bull Island.

The Great South Wall is popular with bathers and birdwatchers. It was the scene of a group nude photograph by American photographer Spencer Tunick, taken on a midsummer weekend in June 2008. The wall has been maintained by Dublin Port, and it hasn’t come cheap, due to the hydraulic effect and movement created by wave action in storms, and exacerbated by the fact that its facing was not sloped, unlike at Dún Laoghaire.

In 1996, Irish Times environment correspondent Frank McDonald reported that it was cracking, and noted that voids had also been discovered at the base of Poolbeg lighthouse. Dublin Port chief engineer Brian Torpey told McDonald that some 27,000 tonnes of granite boulders had been laid on the seaward side of the wall over the previous 10 years, and this "expensive operation" was continuing on the river side, as funds became available.

“If the wall was breached, the channel would be blocked and shipping would be prevented from getting into the port,” Torpey said. “Every year, we used to do a section of the wall, but we have switched attention to the armouring, because of the speed at which it is deteriorating.”

“It was an amazing construction for its time, all built by hand with the aid of tripods,” said Torpey, who added that engineers get “very little kudos” and only “abuse when we want to reclaim some land to develop the port”.

The asphalt plan

Crosbie stresses that Dublin Port’s support is essential for his plan to develop the breakwater as a walkway that is safe under foot. He says that a 2m-wide surface of polymer-enhanced asphalt would make all the difference, and he has already talked to architects and engineers who would carry out the work on a pro bono basis.

“I’d be appealing to contractors and suppliers out there who might contribute materials, and there are technology companies not far from here – Google and Facebook to name but two – who might get involved,” he says. “I’ll put in the planning application and will project-lead it, if there is a public appetite for it out there.” He says he’ll go to Dublin Port with the proposal when he has all the details worked out and a sponsor on board.

Sculptor Patrick O’Reilly has offered to design it as a “piece of art”, Crosbie says, and he believes Capt Bligh deserves a statue – as, perhaps, do the two Pidgeon sisters. Gay Byrne is keen to help in any way he can “to open up this hidden part of Dublin . . .

“It’s a protected structure, and it needs to be handled with respect and dignity,” says Crosbie. “After all, it can be seen from outer space.”