Linda Colley argues that President Putin's invasion of Ukraine is a wake-up call which should remind people that the days of empire are far from over. And these enduring imperial habits, she says, are evident in some unexpected quarters - not just in places like Russia and China.

'When Donald Trump floated the idea of the US purchasing Greenland in 2019, this was widely dismissed as just another Trumpian eccentricity', she writes.

'But this 'real estate deal' as the former president characteristically described his Greenland project, was actually in line with large portions of American history'.

Producer: Adele Armstrong
Sound: Rod Farquhar
Production coordinator: Gemma Ashman
Editor: Richard Fenton-Smith