Kim Longinotto’s Love Is All stitches together short extracts from 75 different films, aiming to highlight changing British attitudes to love, sex and romance. It opens with a one-minute 1899 short which looks forward to the closing shot of Hitchcock's North By Northwest, and the final montage includes scenes from My Beautiful Laundrette and news footage of a same-sex wedding in 2014 Islington. It’s frequently a frustrating viewing experience: the short running-time means that most of the clips are just too brief.

How do you corral 250 films in a way which makes sense to potential viewers? Major releases – so far at this year’s LFF we've had Suffragette, Johnny Depp in Black Mass and Maggie Smith in The Lady in the Van – pretty much take care of themselves. For the mostly unknown rest, festival director Clare Stewart introduced themed strands in 2012 with the stated aim of making the festival “much easier to navigate”.

Director Sarah Gavron tends to make films with strong social content. Her TV movie This Little Life (2003) concerned a couple’s struggles after the premature birth of their son; her first feature film was an adaptation of Monica Ali’s novel Brick Lane (2007) about two Bangladeshi sisters, one confined to an arranged marriage that takes her to London, the other eloping in a "love marriage" in Bangladesh.

It’s somehow unsettling that, while the physical resemblance between Willem Dafoe and Italian writer and filmmaker Pier Paolo Pasolini is remarkable to the point of being almost uncanny, Abel Ferrara’s Pasolini almost consciously avoids elucidating the character of its hero in any traditional sense.

Orson Welles was commissioned by ITV in 1955 to make a 26-part series of travelogues. Always in search of money to fund his independent projects, he was initially enthused by the plan - though predictably he didn’t see it through. Only six episodes were broadcast – none of which stray out of Welles’ favourite European destinations.

Improbably described by the French archivist and critic Henri Langlois as “the greatest technician and the greatest poet of British cinema”, it seems incredible that Richard Massingham isn't better known. A doctor by training, his first shorts were made in the early 1930s as a weekend hobby, and he began shooting promotional and training films to make a living. Twenty two of them are collected here: they’re all highly watchable, the best combining rare technical skill with sardonic humour.

No-one could joke about the tragic aspect of Orson Welles’s career, the fact that his inestimable promise had only been partially realised, better than Welles himself. Once, when asked about the outrage following his panic-inducing radio adaptation of War of the Worlds, the director quipped, “I didn’t go to jail. I went to Hollywood.” And that was punishment enough.

Michael Keaton – like Cary Grant, Bill Murray, and George Clooney – is one of those stars who frequently convey their awareness that the situations they’re in are preposterous. He tautens his jaw muscles; his eyes express a mix of incredulity and suffering. That look is one of the many pleasures of Birdman or (The Unexpected Virtue of Ignorance), 2014’s Best Picture Oscar-winner and Keaton’s crowning achievement as a mature actor.

Among contemporary British documentarists Kim Longinotto has surely travelled the furthest afield internationally – Iran, Japan, Africa – to find her subjects. Love Is All brings her resoundingly back home to Britain, across a timeline that stretches from the very end of the 19th century when the moving image was born, right up to the present day. It’s a fluid anthology about human relations in every form you can imagine, drawn from both more formal feature and documentary films and informal footage from the archives of the British Film Institute and Yorkshire Film.

Cynical writer Macaulay Connor (Jimmy Stewart) and pragmatic photographer Elizabeth Imbrie (Ruth Hussey) are the tabloid team charged with getting the undercover scoop on the society wedding of the year, between old-moneyed Tracy Lord (Katharine Hepburn) and a self-made industrialist. Their way into the party: Tracy’s ex-husband, CK Dexter Haven (Cary Grant). Will Tracy actually marry a social-climbing stiff, or fall for the angry young reporter with an unnatural capacity for champagne? Will Dexter be able to turn the tables on Spy magazine’s diabolical editor?