The High Crusade was produced and executive produced by Ute and Roland Emmerich.
The film stars John Rhys-Davies (who plays the dwarf Gimli in The Lord of the Rings ) and Rick Overton, who also appeared in Eight Legged Freaks as Deputy Pete Willis.
Here's a short synopsis of the film from German-Cinema.de:
A castle somewhere in England. It is the eve of the Crusades, and all good English knights are preparing to march on Jerusalem. Out of the heavens, an alien spaceship descends. An entry hatch opens and a scouting party from another planet emerges, gathering information for a potential march on Earth. The medieval knights are technically underdeveloped, cosmologically misinformed and incredibly thick-skulled. The extra-terrestrials are highly intelligent, technically advanced and extremely knowledgeable. Who will come out on top?
For the knights, there is only one possible reaction to invaders who do not treasure English hospitality: attack. Unimpressed by the aliens' high-tech weapons, the knights storm the spaceship, take a hostage and set off for the Holy Land to put the fear of God into the heathen. But then the hostage switches the automatic pilot to "return home"...