Slow-moving fragments can mean burning debris
Observers said the fragments, which could be seen over parts of Essex and Sussex, were very bright and traced across the sky for up to four minutes.
Robert Massey, an astronomer from the Royal Observatory in Greenwich, said the most likely explanation was burning debris from a Russian rocket or satellite.
"It took a long time to cross the sky and this is characteristic of a satellite or a rocket launcher returning to Earth," he said.
Mr Massey's comments were backed up by Patrick Moore, the presenter of the BBC's Sky At Night since 1957.
He said: "My best guess is that this was debris. There's a lot of it up there."
Some observers said they could even name the origin of the fragments that fell to Earth, believing it to be parts of a Proton-K booster system that launched a number of Russian satellites hours earlier.
Mr Massey said: "It's not as uncommon as most people think. If it's unusually slow moving then it is likely to be debris from space."
One observer, Jay Butler in Brighton, said the fragments were "coloured white and gold".
He had been fishing near Brighton Marina. He said: "The lights appeared in the south east and were heading inland."
Another witness, Bruce Fenton, watched the light-show from Docklands in East London.
Viewing from the side of the River Thames, he said it was "the most spectacular thing I'd ever seen".
At 2230 GMT, he said about eight burning fragments moved east to west across London, taking about four minutes in all, in a brilliant display.
Mr Fenton said that about five minutes later, the surface of the river became very rough with substantial waves hitting the bank.
Many observers believed they were seeing a meteor shower.
The last major meteor event was in mid November, when observers in North America and some areas in the Asia-Pacific region reported seeing streaks of light in the sky every few seconds.