This is Laccaria bicolor - one of the deceivers. Its distinguishing characteristic is the purple down covering the lower part of its stipe.
It grows on nutrient poor, acidic soils and has recently been observed killing and digesting insects (springtails in particular.) It absorbs nitrogen from the springtails and trades it for carbon with neighbouring trees via ecto-mycorrhizal connections.
Here is a clear (if slightly sensationalist) description of the discovery.
