He has been identified with a Richard son of Siward of Farnham in Lower Nithsdale in Yorkshire who around 1215 was pardoned a homicide on his release into the service of a magnate during the war of the barons against King John.

The reason for this is because a Richard son of Siward can be found in the service of William de Forz count of Aumale, a leading Yorkshire baron, in King John's reign.

[1] The 16th-century Glamorganshire antiquary, Rice Merrick, theorised Richard was one of the legendary Twelve Knights whom Robert fitz Hamo settled in Glamorgan after its Conquest, though since that happened before 1100 it is not a serious possibility.

Marshal had spent a large part of his youth fostered in the household of Count Baldwin of Aumale, the stepfather of William de Forz.

[3] In the course of the Barons Wars and the Regency that followed Siward acquired some celebrity, being one of the commanders of the English fleet which defeated the French in the sea battle off Sandwich in August 1217.

Aside from the detailed descriptions of the destruction and booty taken, it was also written that his soldiers "observed one good rule amongst them generally: they did not do any injury or attack any one, except these unjust advisers of the king.

[6] Some measure of his influence with the Marshals at this time is that he was appointed as tutor and guardian of the earl's younger brother Walter, which included wardship of the boy's manors and his castle at Goodrich.

[7] Gilbert Basset moved fast to secure control of her marriage and her lands, which included the barony of Headington and considerable estates in the earldom of Warwick.

This was the result of the overthrow of the justiciar Hubert de Burgh and the installation of a cabal of exiled foreign favourites, led by Peter des Roches, bishop of Winchester.

Hubert de Burgh had been held captive in Devizes castle in Wiltshire, but during October 1233 he had escaped confinement and took refuge in the town church, where he was besieged by royal officers.

On 29 October Siward and a small raiding column appeared and drove off the king's soldiers, who ran in panic thinking Prince Llywelyn or Richard Marshal were upon them.

Siward liberated De Burgh (who he had fought alongside at Sandwich in 1217) and escaped with him to the Severn crossing at Aust where Marshal ships picked him and his men up.

This sort of gesture as much as the daring of his campaigning may help to account for King Henry's notable favour towards Richard Siward following the end of the rebellion.

In 1240 however his nemesis came into his inheritance, the young Richard de Clare, earl of Gloucester and in 1241 his position was weakened by the death of his great ally, Gilbert Basset.

For good measure the earl did the same to Hywel ap Maredudd, and so acquired two of the biggest lordships in Glamorgan by sharp practice, as Siward's attorneys later argued before the king's justices sent into Wales to investigate, in a case which was still going on in the months before his death, which occurred in November or December 1248, by a stroke, according to the historian Matthew Paris.