It was not until the reign of Athelstan that the Cornish kings became subject to the rulers of Wessex: even so the border was established irrevocably on the east bank on the Tamar and in ecclesiastical matters Cornwall was added to the territory of the Bishops of Sherborne.
Under Canute it ceased to be subject to the King of England and only later, at an unknown date in Edward the Confessor's reign was annexed again.
It was until early modern times the general speech of essentially the whole population and all social classes.
Language-shift from Cornish to English progressed through Cornwall from east to west from this period onwards.
From this position the language then inexorably declined until it died out as community speech in parts of Penwith at the end of the eighteenth century.
There is also a surviving religious poem Pascon agan Arluth (The Passion of Our Lord) which enable a linguistic corpus of Middle Cornish to be ascertained.
Later miracle play compositions include: Beunans Meriasek (the Life of St. Meriadoc) datable to 1504; and William Jordan of Helston's Gwreans an Bys (The Creation of the World).
[1] Archived 28 August 2008 at the Wayback Machine The Charter Fragment is a short poem about marriage, believed to be the earliest extant connected text in the language.
[1] Manuscript 1 golsoug ty coweȝ 2 byȝ na borȝ meȝ 3 dyyskyn ha powes 4 ha ȝymo dus nes5 mar coȝes ȝe les 6 ha ȝys y rof mowes 7 ha fest unan dek 8 genes mar a plek 9 ha, tanha y10 kymmerr y ȝoȝ wrek 11 sconya ȝys ny vek 12 ha ty a vyȝ hy 13 hy a vyȝ gwreg ty da 14 ȝys ȝe synsy15 pur wyr a lauara 16 ha govyn worty 17 Lemen yȝ torn my as re 18 ha war an greyȝ my an te 19 nag usy far20 an barȝ ma ȝe pons tamar 21 my ad pes worty byȝ da 22 ag ol ȝe voȝ hy a wra 23 rag flog yw ha gensy soȝ 24 ha gassy ȝe gafus hy boȝ25 kenes mos ȝymmo 25a ymmyug 26 eug alema ha fystynyug27 dallaȝ a var infreȝ dar war 28 oun na porȝo 29 ef emsettye worȝesy30 kam na veȝo 31 mar aȝ herg ȝys gul nep tra 32 lauar ȝesy byȝ ny venna 33 lauar ȝoȝo gwra mar mennyȝ 34 awos a gallo na wra tra vyȝ35 in vrna yȝ sens ȝe ves meystres 36 hedyr vywy hag harluȝes37 cas o ganso re nofferen 38 curtes yw ha deboner 39 ȝys dregyn ny wra40 mar an kefyȝ in danger 41 sense fast indellaKernewek Kemmyn 1 Golsow ty goweth 2 Byth na borth meth 3 Diyskynn ha powes 4 Ha dhymmo deus 5 Mar kodhes dha les 6 Ha dhis y rov mowes 7 Ha fest onan deg 8 Genes mara pleg 9 A tann hi 10 Kemmer hi dhe'th wreg 11 Skonya dhis ny veg 12 Ha ty a'fydh hi 13 Hi a vydh gwre'ti dha 14 Dhis dhe synsi 15 Pur wir a lavarav 16 ha govynn orti 17 Lemmyn y'th torn my a's re 18 Ha war an gres my a'n te 19 Nag usi hy far 20 A'n barth ma dhe bons Tamar 21 My a'th pys orti bydh da 22 Hag oll dha vodh hi a wra 23 Rag flogh yw ha gensi doeth 24 ha gas hi dhe gavoes hy bodh 25 Kyn es mos dhymmo ymmewgh 26 Ewgh alemma ha fistenewgh 27 Dalleth a-varr yn freth darwar 28 Own na borthho 29 Ev omsettya orthis sy 30 kamm na vedho 31 Mara'th ergh dhis gul neb tra 32 Lavar dhiso byth ny vynnav 33 Lavar dhodho gwrav mar mynnydh 34 Awos a allo ny wra travyth 35 Y'n eur na y'th syns dhe vos mestres 36 Hedra vywi hag arlodhes 37 Kas o ganso re'n Oferenn 38 Kortes yw ha deboner 39 Dhis dregynn ny wra 40 Mara'n kevydh yn danjer 41 Syns ev fast yndella 1 Listen friend, 2 Do not be shy!
Pascon agan Arluth ('The Passion of our Lord'), a poem of 259 eight-line verses probably composed around 1375, is one of the earliest surviving works of Cornish literature.