HMS Northumberland, a Royal Navy Type 23 frigate, diverted its course to provide urgent assistance to Dee Caffari and her dismasted 60ft yacht, Aviva, last night in the Bay of Biscay. Northumberland, part of the Nato Response Force that conducts maritime security operations in the Eastern Mediterranean, contacted Andrew Roberts, the director of the Aviva shore team, after a warning was put out by the Spanish coastguard.

Caffari was drifting off the coast of northwest Spain after being dismasted before dawn yesterday. Her ten-year-old boat lost its 100ft mast in 45 knots of headwind and stormy seas 160 miles northwest of La Coruña while heading for the finish of the Transat Ecover B2B race from Salvador de Bahia in Brazil to Brest in France.

A helicopter rescue was planned, but conditions have not worsened, her spokesman said, and Caffari, who had to cut away the rig to stop it damaging the ship, and her shore crew decided that it was safe to stay on board.

Andy Cattrell, the watch manager of Falmouth Coastguard, said: “Whilst this is not a distress situation at the moment, incidents such as this can sometimes deteriorate very quickly into one. We are grateful to the Royal Navy for responding to the call.”

Caffari, was the first woman to sail non-stop single-handed the “wrong” way around the world — west, against the prevailing winds and currents — in 178 days, but it promised to be a gruelling night watching out for collisions in a busy shipping lane. A tugboat to tow her to La Coruña has been arranged, but only for first daylight.

“I was going upwind at eight to nine knots with three reefs in and a staysail and the weather was severe,” Caffari said. “Aviva fell off a wave, landed with a bang and crash, then shuddered. I jumped up on deck to see the mast going over the port side of the boat.”

Caffari, who will head to New Zealand to see her new boat on December 30, has been plagued by mechanical problems on the old Aviva.