Chamber graves in the form of round mounds appeared in the post-Neolithic, pre-Bell Beaker period in Britain and Ireland (and probably the rest of Western and Northern Europe, starting "probably a few centuries after the earliest introduction of domesticated livestock and cereals and the first pottery at the outset of the Neolithic." This is a distinctive typological feature of Neolithic European sites, particularly in areas that were part of the Megalithic movement.
There were a couple of major wave of mound building in this time period, but it petered out in the late Neolithic (towards which time agriculture was also collapsing).
Mound building was only sporadic in the late Neolithic on mainland Britain. One ‘great mound’ – eventually reaching over 35m in diameter and over 6m high – was built over a burial site that had been used repeatedly for centuries at Duggleby Howe in eastern Yorkshire at the start of the third millennium BC. A few round barrows were built over small cemeteries of cremated remains around 3200-3000 BC.
At Killeaba, Ramsey, it seems that a natural mound was used for burial at this time – something that Rachel demonstrated through radiocarbon dating during her PhD research. This site is particularly interesting because the same mound was also used as a burial ground in the Early Bronze Age. In Britain a series of exceptionally large round mounds such as the famous Silbury Hill near Avebury were built near large enclosures such as henges or palisade enclosures late in the Neolithic. These do not seem to have contained burials.
Pre-Indo-European cremation is very unusual in Europe which is why I highlight that passage. The shift from burial mounds to mounds for other purposes is also notable.
There are also Bronze Age mounds which will be discussed at the blog in a future post.
The source is the "Round Mounds of the Isle of Man" blog which is associated with an ongoing archaeological project on the subject, in an increasingly common use of the blog medium.