Jack Hawkins played Ben Manfred, a member of Parliament. Andrew Keir ("Quatermas and the Pit") played his young assistant Jock.
Dan Dailey played Tim Collier, an American foreign correspondent working in Paris. Tim lived on a houseboat in the Seine. Honor Blackman ("Pussy Galore") played his lovely associate Nicole.
Richard Conte played Jeff Ryder, a professor of law at a New York City university that looked like Columbia. Ryder's office had a spectacular view of Manhattan. June Thorburn was his pretty secretary. (Thorburn died in a plane crash at 36.)
Vittorio De Sicca played Ricco Poccari, the owner of a luxury hotel in Rome. Lisa Gastoni ("Cuore Sacro") was his shapely young assistant.
The Four Just Men had worked together on a mission during World War 11, and they pledged at that point to dedicate their lives to righting wrongs. I think this was shown in the pilot episode, which I haven't seen.
This 30-minute series was syndicated in 1959-60. In New York City, it played Thursday nights at 7:00 on WNBC.
Each episode had only one of the four stars, although occasionally there would be a scene where the hero confers briefly with one of the other just men.
This was a production of ITC and Sapphire Films. Sapphire's other series included the superb "Adventures of Robin Hood" with Richard Greene and "The Buccaneers" with Robert Shaw as pirate Dan Tempest.
Sidney Cole was the producer. Cole had produced "The Adventures of Robin Hood", and would go on to produce other first rate ITC shows like "Danger Man/Secret Agent" with Patrick McGoohan and "Man in a Suitcase" with Richard Bradford.
Basil Dearden directed thirteen episodes of "Four Just Men". Dearden was a fine director whose films included "Victim", "Sapphire", "Khartoum", and "Woman of Straw".
"The Four Just Men" is based on a movie that was made in 1921 and then remade in 1939. The movies were based on a novel by Edgar Wallace. In the novel, four British veterans of World War l pledge to use their different professional specialties to fight injustice. They decide that the British Foreign Minister, whose policies they consider dangerously weak, must go. This vigilante aspect of the heroes was not used in the TV series. There is an interesting summary of the book in a review of the 1939 movie on this site.