commonly believed to have been brought to Scotland, in the 4th–5th centuries CE, by settlers from Ireland who founded the Gaelic kingdom of on Scotland's west coast in present-day Argyll. An alternative view has been voiced by archaeologist Dr Ewan Campbell, who has argued that the putative migration or takeover is not reflected in archaeological or placename data (as pointed out earlier by Leslie Alcock). Campbell has also questioned the age and reliability of the medieval historical sources speaking of a conquest. Instead, he has inferred that Argyll formed part of a common Q-Celtic-speaking area with Ireland, connected rather than divided by the sea, since the Iron Age. These arguments have been opposed by some scholars defending the early dating of the traditional accounts and arguing for other interpretations of the archaeological evidence. Regardless of how it came to be spoken in the region, Gaelic in Scotland was mostly confined to until the eighth century, when it began expanding into Pictish areas north of the Firth of Forth and the Firth of Clyde. During the reign of (Constantine II, 900–943), outsiders began to refer to the region as the kingdom of Alba rather than as the kingdom of the Picts. However, though the Pictish language did not disappear suddenly, a process of Gaelicisation (which may have begun generations earlier) was clearly under way during the reigns of and his successors. By a certain point, probably during the 11th century, all the inhabitants of Alba had become fully Gaelicised Scots, and Pictish identity was forgotten. Bilingualism in Pictish and Gaelic, prior to the former's extinction, led to the presence of Pictish loanwords in Gaelic and syntactic influence which could be considered to constitute a Pictish substrate. In 1018, after the conquest of Lothian by the Kingdom of Scotland, Gaelic reached its social, cultural, political, and geographic zenith. Colloquial speech in Scotland had been developing independently of that in Ireland since the eighth century. For the first time, the entire region of modern-day Scotland was called in Latin, and Gaelic was the . In southern Scotland, Gaelic was strong in Galloway, adjoining areas to the north and west, West Lothian, and parts of western Midlothian. It was spoken to a lesser degree in north Ayrshire, Renfrewshire, the Clyde Valley and eastern Dumfriesshire. In south-eastern Scotland, there is no evidence that Gaelic was ever widely spoken. Decline Many historians mark the reign of