Roman Britain in the context of "Maiden Castle, Dorset"

Constantine I (27 February 272 – 22 May 337), also known as Constantine the Great, or known mononymously as Constantine, was Roman emperor from AD 306 to 337 and the first Roman emperor to convert to Christianity. He played a pivotal role in elevating the status of Christianity in Rome, the Edict of Milan decriminalising Christian practice and ceasing Christian persecution. This was a turning point in the Christianisation of the Roman Empire. He founded the city of Constantinople (now Istanbul) and made it the capital of the Empire, which it remained for over a millennium.

Born in Naissus, a city located in the province of Moesia Superior (now Niš, Serbia), Constantine was the son of Flavius Constantius, a Roman army officer from Moesia Superior, who would become one of the four emperors of the Tetrarchy. His mother, Helena, was a woman of low birth, probably from Bithynia. Later canonised as a saint, she is credited for the conversion of her son in some traditions, though others believe that Constantine converted her. He served with distinction under emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces against the Persians, before being recalled to the west in AD 305 to fight with his father in the province of Britannia. After his father's death in 306, Constantine was proclaimed as augustus (emperor) by his army at Eboracum (York, England). He eventually emerged victorious in Civil wars of the Tetrarchy against the emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.

Preston (/ˈprɛstən/ ) is a city on the north bank of the River Ribble in Lancashire, in North West England. The city is the administrative centre of the county of Lancashire and the wider City of Preston local government district. Preston and its surrounding district obtained city status in 2002, becoming England's 50th city in the 50th year of Queen Elizabeth II's reign. Preston had a population of 147,835 at the 2021 census, the City of Preston district 156,411 in 2023 and the Preston Built-up Area 313,322. The Preston Travel To Work Area, in 2011, had a population of 420,661, compared with 354,000 at the previous census. The south bank of the Ribble is part of the Preston urban area, although it forms the South Ribble borough that is administratively separate.

Preston and its surrounding area have provided evidence of ancient Roman activity, largely in the form of a Roman road that led to a camp at Walton-le-Dale. The Angles established Preston; its name is derived from the Old English meaning "priest's settlement" and in the Domesday Book is recorded as "Prestune". In the Middle Ages, Preston was a parish and township in the hundred of Amounderness and was granted a Guild Merchant charter in 1179, giving it the status of a market town. Textiles have been produced since the mid-13th century when locally produced wool was woven in people's houses. Flemish weavers who settled in the area in the 14th century helped develop the industry. In the early-18th century, Edmund Calamy described Preston as "a pretty town with an abundance of gentry in it, commonly called Proud Preston". Sir Richard Arkwright, inventor of the spinning frame, was born in the town. The most rapid period of growth and development coincided with the industrialisation and expansion of textile manufacturing. Preston was a boomtown of the Industrial Revolution, becoming a densely populated engineering centre, with large industrial plants. The town's textile sector fell into terminal decline from the mid-20th century and Preston has subsequently faced similar challenges to other post-industrial northern towns, including deindustrialisation, economic deprivation and housing issues.

Manchester (/ˈmæntʃɪstər, -tʃɛs-/) is a city in Greater Manchester, England. It had a population of over 589,000 in 2024. It is bordered by the Cheshire Plain to the south, the Pennines to the north and east, and the neighbouring city of Salford to the west. The two cities and the surrounding towns form one of the United Kingdom's most populous conurbations, the Greater Manchester Built-up Area, which has a population of 2.87 million.

The history of Manchester began with the civilian settlement associated with the Roman fort (castra) of Mamucium or Mancunium, established in about AD 79 on a sandstone bluff near the confluence of the rivers Medlock and Irwell. Historically part of Lancashire, areas of Cheshire south of the River Mersey were incorporated into Manchester in the 20th century, including Wythenshawe in 1931. Throughout the Middle Ages Manchester remained a manorial township, but began to expand significantly around the turn of the 19th century. Manchester's unplanned urbanisation was brought on by a boom in textile manufacture during the Industrial Revolution, and resulted in it becoming the world's first industrialised city. Manchester attained city status in 1853. The Manchester Ship Canal opened in 1894, creating the Port of Manchester and linking the city to the Irish Sea, 36 miles (58 km) to the west. Its fortune declined after the Second World War, owing to deindustrialisation, and the IRA bombing in 1996 led to extensive investment and regeneration. Following considerable redevelopment, Manchester was the host city for the 2002 Commonwealth Games.

The City of London (often known as the City or the Square Mile) is a city, ceremonial county and local government district in England. Established by the Romans around 47 AD as Londinium, it forms the historic centre of the wider London metropolis. Surrounded by the modern ceremonial county of Greater London, from which it remains separate, the City is a unique local authority area governed by the City of London Corporation, which is led by the Lord Mayor of London; although it forms part of the region governed by the Greater London Authority.

Nicknamed the Square Mile, the City of London has an area of 1.12 sq mi (716.80 acres; 2.90 km), making it the smallest city in the United Kingdom. It had a population of 8,583 at the 2021 census, however over 500,000 people were employed in the area as of 2019.

The Britons (*Pritanī, Latin: Britanni, Welsh: Brythoniaid), also known as Celtic Britons or ancient Britons, were the Celtic people who inhabited Great Britain from at least the British Iron Age until the High Middle Ages, at which point they diverged into the Welsh, Cornish, and Bretons (among others). They spoke Common Brittonic, the ancestor of the modern Brittonic languages.

The earliest written evidence for the Britons is from Greco-Roman writers and dates to the Iron Age. Ancient Britain was made up of many tribes and kingdoms, associated with various hillforts. The Britons followed an ancient Celtic religion overseen by druids. Some of the southern tribes had strong links with mainland Europe, especially Gaul and Belgica, and minted their own coins. The Roman Empire conquered most of Britain in the 1st century AD, creating the province of Britannia. The Romans invaded northern Britain, but the Britonnic tribes such as the Caledonians and Picts in the north remained unconquered, and Hadrian's Wall which bisects modern Northumbria and Cumbria became the edge of the empire. A Romano-British culture emerged, mainly in the southeast, and British Latin coexisted with Brittonic. It is unclear what relationship the Britons had with the Picts, who lived outside of the empire in northern Britain; however, most scholars today accept the fact that the Pictish language was closely related to Common Brittonic.

The Gaels (/ɡeɪlz/ GAYLZ; Irish: Na Gaeil [n̪ˠə ˈɡeːlʲ]; Scottish Gaelic: Na Gàidheil [nə ˈkɛː.al]; Manx: Ny Gaeil [nə ˈɡeːl]) are an Insular Celtic ethnic group native to Ireland, Scotland, and the Isle of Man, and historically, Iceland and the Faroe Islands. They are associated with the Gaelic languages: a branch of the Celtic languages comprising Irish, Manx, and Scottish Gaelic.

Gaelic language and culture originated in Ireland, extending to Dál Riata in western Scotland. In antiquity, the Gaels traded with the Roman Empire and also raided Roman Britain. In the Middle Ages, Gaelic culture became dominant throughout the rest of Scotland and the Isle of Man. There was also some Gaelic settlement in Wales, as well as cultural influence through Celtic Christianity. In the Viking Age, small numbers of Vikings raided and settled in Gaelic lands, becoming the Norse-Gaels. In the 9th century, Dál Riata and Pictland merged to form the Gaelic Kingdom of Alba (Scotland). Meanwhile, Gaelic Ireland was made up of several kingdoms, with a High King often claiming lordship over them.

Flavius Valerius Constantius (c. 250 – 25 July 306), also called Constantius I, was a Roman emperor from 305 to 306. He was one of the four original members of the Tetrarchy established by Diocletian, first serving as caesar from 293 to 305 and then ruling as augustus until his death. Constantius was also father of Constantine the Great, the first Christian emperor of Rome. The nickname "Chlorus" (Ancient Greek: Χλωρός, lit. 'the Pale') was first popularized by Byzantine-era historians and not used during the emperor's lifetime.

As an Illyrian soldier of humble origin, Constantius had a distinguished military career and rose to the top ranks of the army. Around 289, he set aside Helena, Constantine's mother, to marry a daughter of Emperor Maximian, and in 293 was added to the imperial college by Maximian's colleague Diocletian. Assigned to rule Gaul, Constantius defeated the usurper Carausius there and his successor Allectus in Britain, and campaigned extensively along the Rhine frontier, defeating the Alamanni and Franks. When the Diocletianic Persecution was announced in 303, Constantius ordered the demolition of churches but did not actively hunt down Christians in his domain. Upon becoming senior emperor in May 305, Constantius launched a successful punitive campaign against the Picts beyond the Antonine Wall. He died suddenly at Eboracum (York) in July the following year.

Eboracum (Classical Latin: [ɛbɔˈraːkũː]) was a fort and later a city in the Roman province of Britannia. In its prime it was the largest town in northern Britannia and a provincial capital. The site remained occupied after the decline of the Western Roman Empire and ultimately developed into the present-day city of York, in North Yorkshire, England.

Two Roman emperors died in Eboracum: Septimius Severus in 211 AD, and Constantius Chlorus in 306 AD.