In Hampstead acting veteran Diane Keaton plays Emily, a recent-widow in late middle-age, whose only inheritance is a tower of debt and bitter memories of her husband’s infidelity. She has an adult-son, Philip (James Norton), who holds his deceased father in high-esteem, something Emily never tries to blemish.

Emily lives evasively: despite her financial woes, she maintains an infrugal lifestyle and continues to volunteer at a charity shop, hoping the accountant with a romantic agenda could pull her out of the mire. In the attic she stumbles upon a pair of binoculars that she uses to spy on Donald (Brendan Gleeson), a vagrant, in a shrubland across the road.

Having occupied the block of disused site for 17 years, the Irishman has set up a comfortable shack where he grows his own food, generates his power. But, because Hampstead Heath has become prime real estate, Donald finds himself served up with eviction notices and physical threats.

Based in part on a true story around Harry Hallowes, a homeless man, who in 2007 challenged squatter-removal orders in the courts and won, this new feature by Joel Hopkins is a feather-light love-comedy. Here, Donald is an endearing mixture of stubborn-gruff and vulnerability and tenderness, one who after succumbing to human weakness in the past is determined to keep his home and way of life.

Keaton gives Emily the idiosyncracies and flightiness of a woman longing to be swept off her feet in her silver-years. The broken heart she suffers when the man she loves resists her plans for their future is convincing.

Yet, while some may find Hampstead heart-warming — even cute — the serendipitous encounter feels too much like a plot mechanism, short on persuasion (and weight).