Captain McAlpine led the project on Tristan Da Cunha, which included a team of 150 Servicemen and women, 34 Royal Engineers and other port and maritime staff.

They took 400 tonnes of cement from the UK and mixed it with crushed local volcanic rock to make the concrete required to repair the harbour.

Enough concrete was made to fill Chichester's Westgate swimming pool.

Tristan Da Cunha lies 1,750 nautical miles from Cape Town and 2,200 from Rio De Janiero. The island has a population of just 290 and relies on the small harbour as its only source of trading.

Captain McAlpine said he was 'delighted' with the effort. "The repairs should last many years," he said.

He is now home with his wife Janette, who works at Central School, his daughter Emily (eight), a pupil there, and son Harry (13), a Bishop Luffa student.