My first answer to this year's challenge:mainleftrightback
In the early fifth century the Roman Empire was under pressure, harsh winters across Europe meant that more and more Barbarians were crossing the Rhine into the Empire. Emperor Constantine was forced to withdraw troops from Britain in order to combat these attacks, leaving Britain open to invasions of Angles, Jutes and Saxons. The Romans had given Britain an infrastructure and population levels that would not be rivalled again until the Medieval period, but all this soon began to crumble as Britain entered the Dark Ages.
I know I said I didn't have enough bricks for a primary colour castle, but then this came to me - inspired by one of my favourite Anglo-Saxon poems, the Ruin
"Roofs are fallen, ruinous towers,
the frosty gate with frost on cement is ravaged,
chipped roofs are torn, fallen,
undermined by old age."
Thanks for looking!