Discovered separately, but almost simultaneously, by two astronomers in July 1995, the comet is already visible in the early morning in the north-east sky. But as this month continues it will become visible at night, too, in the north-west, until it should be possible to see it - streetlights and fog permitting - during the evening. Astronomers expect that it will develop a long tail which will make it a clear feature of the night sky. "It looks like a bright, hazy star with a short tail," said Robin Scagell, vice-president of the Society for Popular Astronomy. "The best time to look is about 5am, before the dawn gets too bright."
The comet, a 400-kilometre-wide ball of ice and dust and chemicals, will be at its closest to Earth on 22 March, when it will be 125 million miles away.
It will be closest to the Sun on 1 April, at a distance of 85 million miles.
Then it will continue on its elliptical orbit towards outer space again.
"It will be one of the most spectacular comets of our lifetime," said Dr Alan Fitzsimmons, astronomer at Queen's University Belfast. "But then we don't know when the next one will appear."