The chaplain came on board at St John's, Antigua, with the role of being "a friend and adviser, and a listening ear, to all on board and to any Montserratians I can help".
Ms Theakston, a leading figure in the fight to have women ordained, said she felt close to the islanders because there were many Montserratians in her earlier Anglican church congregation of St John at Hackney. "I have two bosses, God and the captain," she said.
The 4-5,000 Montserratians still on the island are increasingly complaining of stress, not only over the threat of another major volcanic eruption but because of cramped living conditions in the tiny northern zone where they are now squeezed.
The 250-member crew of the Liverpool, including around 30 women, are suffering mainly from a continuing cloudstream of black volcanic ash, which gets into the eyes and throat. The ash was particularly thick on Tuesday as Captain David Snelson took the ship past the abandoned capital of Plymouth, now a light grey wasteland of boulder-battered, burnt-out and ash-covered buildings.
The HMS Liverpool came to Montserrat to supervise the "voluntary evacuation" of those of the remaining islanders who opted to leave for nearby islands or Britain. But as the volcano quietened down last week, most people opted to stay. "We came here expecting a large evacuation that hasn't happened," Captain Snelson said. "There are more people going back to Montserrat than leaving," according to one of his officers.
Although 1,000 islanders registered for the evacuation, only 35 left during the first three days. There have usually been at least that number on the daily ferry going in the opposite direction. Some of these are relatives coming back to help their families pack. Others are evacuees who are now more confident the volcano will not affect the north of the island and that it will be developed with British aid.
"We have made some changes. When we announced yesterday that people would be able to get their airline tickets [from Antigua to Britain] here on the island, a cheer went up," said Mary Strode, of the aid management office of the Department for International Development. "We think that system will be more popular and it saves us money on Antigua hotels. People didn't like the idea of going to Antigua and waiting."