It's well known that George RR Martin's series of novels A Song of Ice and Fire, from which TV show Game of Thrones is adapted, is based on Medieval British history. The 15th century War of the Roses is the most obvious example, the houses of Lancaster and York echoed in the battle between Westeros' houses of Lannister and Stark.
As this Guardian article points out, there's also bountiful parallels between characters from the show and other real-life historical figures and events too.
Like Robert Baratheon and King Edward IV, Ned Stark and Richard Duke of York, Cersei Baratheon and French princess Margaret of Anjou, the Night’s Watch and the Knights Templar, and many more.
In a recent video called "The Real Life Game of Thrones Part 1: Is Great Britain Westeros?" YouTuber RealLifeLore explores these and some other similarities between Westeros and aspects of British history—minus the dragons, giants, tree children, and ice gods though.
One of the biggest revelations is that not only do the narratives and characters echo the history of the Medieval British Isles, but the map of Westeros is basically the British Isles too—just shifted around a bit.
As you'll see in the video and the GIF below, if you take Ireland, place it below England, then turn it 180 degrees and attach it to the South coast of England, then mirror flip England you basically get Westeros.
Like, WHOAH. They're not entirely exact but they're very, very similar.
The video also points out there was a wall, just like The Wall in the show, built in Britain to keep out unwanted wild folk. It was called Hadrian's Wall and was created by the Romans, and George RR Martin has already stated in an interview with Rolling Stone that it served as the inspiration.
In fact he says it was the seed that generated the entire series after he visited it in 1981. "The Wall predates anything else." he says. It got him thinking about how the Romans might have conceived that beyond that wall could have been anything: monsters, beasts, mythical beings—all that was actually beyond it was the Scottish.
The video also explains how England from the 5th to the 10th century was split into seven kingdoms, another parallel with the series as Westeros is referred to as the Seven Kingdoms. The similarities are manifold, it's fascinating, and if you're a fan of the show the video's essential viewing.