J.J. Marric is the pseudonym of John Creasey.
"A General Election was imminent, which meant more work for Commander Gideon of Scotland Yard. Eve of Poll rallies were scheduled for November 5th, and that was too significant a date in Parliamentary history to be comfortable. Today the House of Commons had new enemies whose fanaticism was equal to that of Guy Fawkes so long ago. And if they had modern weapons in their hands, they could destroy on a far vaster scale...
A top nuclear scientist went missing, along with a vital piece of atomic equipment. And as the crowds amassed for the greatest peace rally ever held, only Gideon knew the true irony, and appalling danger, of the situation. For those enemies now had the power to destroy London at the press of a button." - Hodder & Stoughton jacket notes, 1977 edition.
Somewhat dated, but still a good plot and suspense. First published in 1964. ( )