Leading article: The best sort of invasion

Intervention on the far side of the world has a controversial reputation. Over the last 20 years passionate supporters and opponents have clashed over the morality of the actions. However the announcement of the launching of a task force, a ship and two helicopters carrying lethal weapons, setting out for the Pacific makes a strong case for its potential efficacy.

The Royal Society for the Preservation of Birds has for many years been concerned about the fate of a rare species, the Henderson petrel, whose only home and breeding ground is Henderson Island, a tiny uninhabited part of the Pitcairn overseas territory.

More than 3,000 miles from the nearest land, it is also home to more than 55 unique species, including four land birds, eight species of snail and nine plants. It became a World Heritage site in 1988; the world's only forested atoll with its ecology virtually intact. However the explosion in the rat population, first introduced by visiting Polynesians, has been devasting for the other inhabitants.

Where once there were millions of Henderson petrels, now there are less than 40,000. The RSPB's task force intends to exterminate the rats and thus secure the future of this unique habitat and its astonishing variety of flora and fauna.