First, about the DVD - it's a low budget copy, mono soundtrack with no extras to note. This spoils somewhat the overall enjoyment of the film.
Second, about the film - it's a quick paced farce set on a train and in two fixed locations. Now if this sounds uninspiring it shouldn't be. It is really quite a funny film. Though slightly silly at times it keeps you following who is who as the plot untwines.
Finally, a note about the actors - Michael Caine and Roger Moore are great in their roles, making a good duo and supporting actors plays their part well too.
Though not a well known film and probably never destined to be a classic, it is a welcome breath of fresh air from serious films because it is first and foremost entertaining. I like it, but there again I like Marmite too - it's probably one of those kind of films. I suggest you buy it if you like the actors but avoid it if not.