Julius Caesar discusses the island of Britain and its people in his account of the Gallic wars.
Gaius Julius Caesar invaded Britain twice – in 55 and 54BC.
The first of these incursions was little more than a reconnaisance mission, which established a beachhead on the Kent coast but went no further. The second proved more enduring, resulting in the defeat of Cassivellaunus, and his replacement with the more Roman-friendly Mandubracius.
But having won a military victory, the Romans then left Britain. They would not return until 43AD, when Britain was incorporated into the Roman Empire. It would remain a colony of Rome until the last legions were withdrawn in 410AD.
This description of Britain was given by Julius Caesar in his account of the Gallic wars
See also Caesar’s description of the invasion of Britain and Caesar’s account of the war and his departure from Britain.
Julius Caesar on Britain, 54BC
The interior portion of Britain is inhabited by those of whom they say that it is handed down by tradition that they were born in the island itself: the maritime portion by those who had passed over from the country of the Belgae for the purpose of plunder and making war; almost all of whom are called by the names of those states from which being sprung they went thither, and having waged war, continued there and began to cultivate the lands. The number of the people is countless, and their buildings exceedingly numerous, for the most part very like those of the Gauls: the number of cattle is great. They use either brass or iron rings, determined at a certain weight, as their money. Tin is produced in the midland regions; in the maritime, iron; but the quantity of it is small: they employ brass, which is imported. There, as in Gaul, is timber of every description, except beech and fir. They do not regard it lawful to eat the hare, and the cock, and the goose; they, however, breed them for amusement and pleasure. The climate is more temperate than in Gaul, the colds being less severe.
The island is triangular in its form, and one of its sides is opposite to Gaul. One angle of this side, which is in Kent, whither almost all ships from Gaul are directed, [looks] to the east; the lower looks to the south. This side extends about 500 miles. Another side lies toward Spain and the west, on which part is Ireland, less, as is reckoned, than Britain, by one half: but the passage [from it] into Britain is of equal distance with that from Gaul. In the middle of this voyage, is an island, which is called Mona: many smaller islands besides are supposed to lie [there], of which islands some have written that at the time of the winter solstice it is night there for thirty consecutive days. We, in our inquiries about that matter, ascertained nothing, except that, by accurate measurements with water, we perceived the nights to be shorter there than on the continent. The length of this side, as their account states, is 700 miles. The third side is toward the north, to which portion of the island no land is opposite; but an angle of that side looks principally toward Germany. This side is considered to be 800 miles in length. Thus the whole island is [about] 2,000 miles in circumference.
The most civilized of all these nations are they who inhabit Kent, which is entirely a maritime district, nor do they differ much from the Gallic customs. Most of the inland inhabitants do not sow corn, but live on milk and flesh, and are clad with skins. All the Britains, indeed, dye themselves with wood, which occasions a bluish color, and thereby have a more terrible appearance in fight. They wear their hair long, and have every part of their body shaved except their head and upper lip. Ten and even twelve have wives common to them, and particularly brothers among brothers, and parents among their children; but if there be any issue by these wives, they are reputed to be the children of those by whom respectively each was first espoused when a virgin.
Source: The Gallic Wars V, by Julius Caesar, translated by W. A. McDevitte and W. S. Bohn
Go to Part III of Caesars’s account of the invasion of Britain.