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disputed land frontier became a battle zone once again, as it had been during the first years of the
Roman occupation. This time the enemy were the Saxons, who had arrived in England in the
middle of the fifth century and who, like the Irish, took advantage of the power vacuum left behind
when the Romans departed. There is more to come on the Saxons and their genetic legacy when we
travel to England, but for the time being we need only know that their westward expansion was
effectively halted at roughly the same frontier that the Romans had defined with their lines of
legionary forts.
The boundary was formally marked out in the late eighth century by Offa’s Dyke, named after
the Mercian king responsible for its construction. Unlike Hadrian’s Wall, Offa’s Dyke was not a
fortified frontier barrier with regularly spaced garrisoned forts, but an earthwork built to denote
rather than to defend the frontier, though in its construction it was far more than a boundary fence.
Offa’s Dyke consisted of an earth embankment up to 3 metres high and backed by a ditch up to 20
metres wide. The boundary it defines stretched for 240 kilometres from Prestatyn on the north coast
to Beachley near Chepstow on the Severn Estuary. The Dyke marks this boundary for 130
kilometres, the rest being defined by natural features like the River Severn. Though it is built only
of earth, thousands of men must have been involved in its construction, proof of the level of
organization in the kingdom of Mercia at the time.
The Saxons did not advance far beyond the Dyke but, as you might by now expect, it proved to
be a fluid boundary. Though the construction of the Dyke coincided with the beginning of the Viking
Age, the Welsh kings did not respond by uniting under one leader as the Celts and Picts had done in
Scotland. The Welsh never did regain the lost lands in England on behalf of the Britons, though not
always through want of trying. In 633 Cadwallon launched a counter-attack against the Saxon King
Edwin, whose title Bretwalda at least claimed control of the whole of Britain. Edwin had attacked
Anglesey, but Cadwallon drove him back into England and eventually defeated and killed him at
the battle of Meigen near Doncaster. He then killed Edwin’s heirs, Osric and Eanfrith, and,
according to Bede, it was his intention to exterminate the whole English race. He had his best and
only chance in 633 for, the following year, he was himself killed by Eanfrith’s brother. As we shall
see, the memory of Cadwallon’s near success was to shape things to come.
We have seen what a significant genetic effect the Viking settlements from the late eighth
century onwards have had in Scotland. Can we expect the same in Wales? Although the Vikings
soon dominated the western seaways and had, by 830, begun to set up colonies at Dublin and other
Irish coastal towns, there is very little evidence of them having succeeded in colonizing Wales. In
the north they were actively repelled by Rhodri Mawr (Rhodri the Great), King of Gwynedd, who
defeated a Danish attack on Anglesey in 856.
Only in the far south-west is there any suggestion of Viking settlement. It is there, as we saw in
an earlier chapter, that the high levels of blood group A have been used to argue for a substantial
Viking settlement in what is now Pembrokeshire. We shall certainly see if we can find
corroborative evidence when we look at the genetics. Based on the experience in the Northern
Isles, if Viking genes are there in large numbers we will certainly find them.
The Welsh kings continued in their internecine wars, sometimes making alliances with the
Saxon kings against one another. So long as they were busy fighting between themselves, they were
no threat to England. Only once did they unite under a single ruler, and then only for six years.
Gruffudd ap Llywelyn began as the King of Gwynedd and it was from this position that he launched