A band of medieval knights assemble for a joust in the grounds of his mansion house, but they have more on their mind that simple sport: they are out for justice. They gather around the two participants, but while one seems keen to get on with it, the other is pleading for mercy, which falls on deaf ears as they put him on a horse and force him to ride towards his opponent, but he has no training in this activity and is quickly knocked to the ground. The knight dismounts and comes at the hapless victim with a mace, smashing his head in and leaving him for dead as the others look on approvingly. However, the actual Lord of the Manor (Peter Cushing) suddenly arrives and is horrified to see what he thinks is an accident...
Which is why he only appears once more in the film, and that in flashback (actually Cushing was at a loose end after a different project fell through, hence his brief guest star bit here). But the actor playing his son, Sir John Gifford (American import David Birney), jets in on a transatlantic flight to hear the reading of the will, only to find ex-police commissioner Colonel Bertie Cook (John Mills, an actual knight in real life) waiting for him with valid suspicions that his father was murdered. Part of the lack of tension inherent in that plot was that it was obvious those knights we saw at the start, led by Sir Giles Marley (Donald Pleasence), were up to no good therefore we were simply waiting around for the heroes to catch up to what we were already aware of.
Perhaps that, accompanied by a premise that could have been played straight yet in practice was rather goofy, was the reason Trial by Combat was so looked down on when it was originally released, and ever since for that matter, as aside from a few television showings it doesn't appear to have lodged itself in too many memories. That said, there is a good case for it being underrated, for the sense of humour it did have may have been irreverent but it did serve to highlight its target of the reactionaries in British society who feared it was going to the dogs and an active intervention by force was going to be necessary. This wasn’t counterculture conspiracy theorising, there were genuine elements high up well prepared to stage a coup as Britain sank under debt and social unrest.
Exactly how they would have taken to being depicted as a bunch of crypto-fascist nutcases wedded to a notion of chivalry that essentially gave them carte blanche to murder anyone who offended their sensibilities went unrecorded, but for all the jokey, eccentric tone it did lend an edge to the thriller narrative in a way that many observers identified as harking back to the sort of adventure John Steed and Mrs Peel would tackle back in the previous decade in television series The Avengers. Though this didn't reach that level of the classic programme, they were cut from similar cloth, and Mills in particular was having fun as the sort of elderly agent Steed may have become (though in actuality Patrick Macnee was relegated to the indignities of accompanying James Bond in A View to a Kill).
It presented these villains, who murdered those they felt had got off too lightly for their supposed crimes, in a most curious tone, a humourless bunch who picked on those they could get away with killing because they knew it was really no contest once the armour was on. Also showing up for reasons best known to themselves were Barbara Hershey, who is involved in a chase between a Mini Clubman and some violent, pikestaff-wielding bad guys on horseback (she was in the car), Brian Glover who was highly amusing as a mummy’s boy gangster handy with his fists when his time came, and respected stage actress Margaret Leighton as his mummy, in the final role before her death and proving no pushover. All good fun (apart from Glover's gratuitous gay slurs), but it was Mills who carried it whether he was filling John Savident's New Scotland Yard office with pigeons or chatting with a monkey in a pink woollen suit (the monkey, not Sir John), the Colonel’s preference for animals over people part of his crusading personality. There wasn't much else like this around at the time, nor has there been since, and if it wasn't to everyone's taste those with a liking for the offbeat would find plenty to appreciate. Music by Frank Cordell.