Monster momma tears up London to rescue her offspring, who has been captured and put on exhibit in a circus.
Britain's answer to Godzilla is not bad; not as good as Gojira, but not nearly as bad as Reptilicus. The mother-child aspect is what makes this one special, and helps it rise above some plot missteps and greivous misuse of stock footage (the Royal Navy didn't fly US Navy Panthers). The third such film directed by Lourie, and unfairly maligned on Mystery Science Theater 3000 (something which just highlights that show's later slide into asininity rather than defects of the movie in question). Interesting to see nice guy Travers playing against type as a money-hungry jerk. And the kid (Winter) who's wiser than the adults prefigures the know-it-all brats that became a staple of the Japanese Gamera films. Whatever other problems the film has, the London destruction scenes have a realisitc brutality that helps makes up for them.
An honest assessment would be helped by a DVD transfer that didn't looks like someone's old home movies. VCI's 2005 disc is absolutely terrible, and should be avoided. "Digital remastering" does not mean sharpening the print to the point everthing is haloed. The mono sound has been converted to stereo, with annoying background noise added, like the non-native American Robins calling in the background of the Irish scenes, as well as cheesy overdubbing of the naval gunfire scenes. Hopefully the upcoming BluRay will be from new elements, as promised.
Note: Murray Kash and Ed Bishop overdubbed all the stock footage of naval aircraft and ships, something which might be jarring to UFO fans!
Thanks to Philly for identfying many unknowns!