After the Romans vacated the British Isles at the end of the 4th century, the Welsh or Ancient Britons were left in sole possession of all of England, all the way north to the banks of the Clyde. Their most distinguished leaders were Ambrosious, and later in the 5th century, King Arthur of the Round Table. The Saxons forced them westward into the mountains of what is now Wales, north to Cumberland and southern Scotland, and into Cornwall to the south. The first recorded King of Wales was Rhodri Mawr, or Roderick the Great who ruled from his seat in Anglesey. He died in 893. On his death, he gave Wales to his three sons, Anarawd became King of North Wales, Cadalh became King of South Wales and Mervyn became King of Powys, or mid Wales.

The ancient history of the name Mathew also emerged from these same Welsh chronicles, woven into the prosaic tapestry of the ancient Welsh heritage. It was first found in Glamorganshire where they were seated from early times and their first records appeared on the early census rolls taken by the early Kings of Britain to determine the rate of taxation of their subjects.

Researchers reviewing various manuscripts such as the Domesday Book, the Pipe Rolls, Hearth Rolls, the Black Book of the Exchequer, the Curia Regis Rolls, finding that the name Mathew was found in many different forms. Althought the surname Mathew occurred in many references, from time to time the surname was spelt Mathews, Mathew, Matthews, Mathewes, and many of these versions are still in use today. These changes in spelling frequently occurred, even between father and son. It was not uncommon for a person in his or her own lifetime to be born with one spelling, marry with another, and have still another on the headstone in his or her resting place.

The Norman Conquest of Wales was a disaster. A testimony to the indomitable Welsh fighting spirit is that there are more castles, or ruins of castles, to the square mile in Wales than anywhere else in the world. Border warfare against the Normans and their successors continued unabated until the end of the 14th centruy. The Welsh tactic was to thrust, then retire to their bleak mountain homes to plan their next attack. As peace gradually returned to theis picturesque country, the Welsh, attracted by the economic opportunities, moved eastward into the English cities. Hence, we now find Welsh surnames such as Mathew, Jones, Price, Edwards, Phillips, Evans, Pritchard, Morgan, Williams, Roberts, Davis and so on, to be amoungst the most populous families in England at this time.

In this background of mountain greenery the Welsh family name Mathew emerged as a notable family name in Glamorgan where recorded as a family of great antiquity seated with manor and estates in that shire. This distinguished Welsh family claim descent from Yvorc, (Elvorach) or (Ivor bach), Lord of Torkelyn, in Anglesey, who came to the assistance of Jystyn Ap Gurgant, Prince of Glamorgan and received large grants of land in that county. Sir David Mathew of Llandaff became Grand Standard Bearer to King Henry VI and the name flourished in England by many branches, including the Mathews of Stanstead, Mathews of Tresunder in Cornwall, St. Kew in Cornwall, in Herefordshire, in Essex and Middlesex. However, the senior line remained at Castle Menych. They became the Earls of Llandaff. Prominent amongst the family name during the late middle ages was Earls of Llandaff.