An Absolute Stinker I first saw this movie when it was shown in my high school about 2 or 3 years after it was released. I wasn't impressed with it back then. I watched it again this weekend and my opinion of it is even lower now.
First of all, the movie is full of technical inaccuracies. The Germans had helicopters that wouldn't appear until the late 1950s/early '60s? Really? (Wouldn't landing a chopper in such a small courtyard be considered dangerous, even for military pilots? Being a metre or so off in any direction would mean that the rotors would clip the stonework, resulting in a mishap.)
The use of the radios was also laughable. The size of the rig that the group took with them was what we hams would call a boat anchor because it's large, bulky, and heavy. (Transistors wouldn't be invented until the late 1940s.) Because it's supposed to be a covert mission, wouldn't something smaller and lighter have been more appropriate? From my understanding of what was used for such purposes during WW II, the radio should have only been capable of sending Morse code. There wouldn't have been the need for any of the circuitry required for voice transmissions.
Then, because it was supposed to be a covert mission, why was Richard Burton's character transmitting in the clear? Shouldn't he have used code words to disguise the content and purpose of the transmission? That in itself would be another reason to used a Morse code rig as it would have been easy to encrypt the message by using a cipher. Besides, using encryption would add to the mystery of the mission for the viewers. On top of that, Morse code transmissions would have had a better chance of being received in England.
I guess Alistair MacLean, as well as the movie's producers, probably thought that the audience would be too dumb to figure that out.
The plot itself is full of holes. For example, since when does a covert operations team deploy only hours after, apparently, being assembled for the first time? Nobody seemed to know who anybody else was, which would hardly be conducive to the group's effectiveness.
Of course, all those crack German troops that were stationed near the castle couldn't hit the broad side of a barn whenever they were shooting. All of their motor vehicles exploded and burned instantly at even the sound of gunfire and the drivers seem to find every bump, pothole, and obstacle even in broad daylight.
I could go on, but I'm sure you get the picture.
I read a number of MacLean's novels while I was in junior high and I thought he was a pretty good author. But it was around the time that this movie was made that the quality of his writing, in my opinion, started declining. He started by telling some good stories but eventually they became predictable potboilers. Change some names and settings, and one could easily figure out how it was going to end. I gave up after I read "Bear Island", which I thought was rubbish.
Avoid "Where Eagles Dare", but, if you want to see a good movie in which Richard Burton plays a spy, watch "The Spy Who Came In From The Cold", which was made a few years earlier. It's a good story and has lots of plot twists to keep you guessing.