Early Man
The biggest threat to many of the animals of this time would have been humans.
Humans were present in Britain at various times from around 700,000 years ago.

The picture above shows a piece of Reindeer antler that has had regular cut-marks made along its length. This would have been done by a human with a stone tool around 40,000 years ago.
For more on humans in Britain, visit the Ancient Human Occupation of Britain website