"Fleet St. bang" - Could have been 'Dicky' Martin in Javelin (WT830?? )
Profile 179 page 6 states
" Shortly afterwards (Martin replacing Waterton - my italics) sonic bangs were heard for the first time from a Javelin. This was not publicly demonstrated, and at the time there had been a lot of adverse comment about the long Javelin development programme and the lack of results. On the night of 4th. July (1954) many thousands of Londoners heard the bang of a Javelin's supersonic passage. Mr. Maudling, then Minister of Supply, explained to the House on 11th. July that "the aircraft was cruising at high altitude and near the speed of sound when the pilot's oxygen supply suddenly failed; during the ensuing confusion he inadvertently exceeded the speed of sound causing the bang".
Apologies for extending the thread creep, but does this fit the scenario ?