Battle of Deorham The Battle of Deorham or Dyrham was fought in 577 between the West Saxons under Ceawlin and Cuthwine and the Britons of the West Country . The location , Deorham , is usually taken to refer to Dyrham in South Gloucestershire . The battle was a major victory for the West Saxons , who took three important cities , Glevum ( Gloucester ) , Corinium Dobunnorum ( Cirencester ) and Aquae Sulis ( Bath ) . The battle is known exclusively from the " Anglo - Saxon Chronicle " , which gives few details , but it is thought to have been a major engagement . Account . The " Anglo - Saxon Chronicle " entry for 577 records that that year King Ceawlin of Wessex and his young son Cuthwine fought the Britons of the West Country at " the spot that is called [ Deorham ] " . This is generally taken to be Dyrham in what is now South Gloucestershire , on the Cotswolds escarpment a few miles north of Bath . The West Saxons carried the day , and three kings of the Britons , whose names are given as Conmail , and Condidan , and Farinmail , were slain . As a result of the battle , the West Saxons took three important cities , Glevum , Corinium Dobunnorum and Aquae Sulis , representing a fairly substantial area of Gloucestershire and Somerset . Presumed strategy and tactics . The Severn Valley has always been one of the military keys of Britain , and some of the decisive battles of the Saxon conquest were fought to control it . In 577 Ceawlin advanced from the Thames Valley across the Cotswolds to seize the area and break the power of the Britons in the lower Severn area . Some historians ( such as William St . Clair - Baddeley in 1929 ) have concluded that the Saxons may have launched a surprise attack and seized the hill fort at Hinton Hill Camp ( Dyrham Camp ) because it commanded the Avon Valley and disrupted communications north and south between Bath and her neighbouring Romano - British towns of Gloucester and Cirencester . Once the Saxons were in occupation of the site ( and had begun reinforcing the existing Iron Age defensive structures at the site ) the Britons of those three towns were compelled to unite and make a combined attempt to dislodge them . Their attempt failed and the three opposing British kings were killed ( they are named as Commagil of Gloucester , Condidan of Cirencester and Farinmagil of Bath ) . Their routed forces were driven north of the River Severn and south of Bath where it appears they began the construction of the defensive earthwork called the " Wansdyke " in a doomed attempt to prevent more territory from being lost . The military historian Lieutenant - Colonel Alfred Burne , employing his theory of ' Inherent Military Probability ' opted for a simpler explanation for the battle than Clair - Baddeley . In his view Ceawlin was methodically advancing towards the Severn and the three forces of Britons concentrated to stop him . Burne suggests that they formed up along two slight ridges across the trackway that skirted the Forest of Braden , with Hinton Hill Camp behind them as their stores depot – a position similar to that adopted at the Battle of Beranburh in AD 556 . Burne pointed out that if the Saxon attack drove the Britons back from their first line onto the second ridge near the edge of the escarpment , the slightest further retreat would leave their flanks open to a downhill pursuit . He speculates that this is what occurred , with the three Briton leaders and their main body being driven back into the fort while the flanking Saxons driving forwards swept round behind the promontory on which the fort stands . A last stand in this position would explain why none of the three Briton leaders was able to escape . Outcome . The battle was won by the Saxons , who afterwards occupied the three cities of Cirencester ( Corinium ) , probably a provincial capital in the Roman period , Gloucester ( Glevum ) , a former legionary fortress and a colonia , and Bath ( Aquae Sulis ) , a renowned pagan religious centre and spa - city . The remains of many villas are found around these cities , which suggests that the area was both wealthy and relatively sophisticated , and thus that this Saxon advance was a heavy blow to the Britons . The battle is also considered by some to have begun the differentiation of Welsh and Cornish into two separate languages , by cutting off the Britons in Wales from those in Devon and Cornwall , by land . Against this , it has been objected that , although the battle may have prevented large - scale movements , the passage of British - speakers between the two areas seemingly stayed possible , given that a Welsh genealogy appears to record that , in the 7th century , the descendants of kings of Pengwern founded a dynasty in the Glastonbury region . The journey by boat would not be difficult . Further , archaeology suggests that , although the Anglo - Saxons quickly took over the Cirencester region after the battle , it took many years for them to colonise Bath and Gloucester as well . Even if it did not lead to a language separation , Deorham was militarily decisive in cutting the Britons of South West England off from their fellow - Britons of the English Midlands , who were soon to be conquered by the Angles of Mercia .