In this, the fourth episode in the series, continuing immediately from the end of 'Waterloo', Tracy and the Commander are hoping for a nice quiet end to their wedding day but they are soon to find that is the last thing they will get.
A mysterious car following them quickly arouses the Commander's suspicions and this soon leads to revelations that he and Tracy may be in personal danger.
Against this background, the President of the United States of America comes to visit London. Aside from the usual chaos such visits usually bring, there are other forces at work and although it looks like they are targeting the President and his aides, it quickly becomes apparent that their presence is only secondary.
The fourth novel in the series is also the shortest but is important as we are introduced for the first time to a new regular character Sir Richard Crowthorne who becomes a very important feature as the series of novels develops.
Quite a few different locations feature as the series ventures to the far north western extremities of the Metropolitan Line including Harrow on the Hill, Chesham, Chalfront & Latimer and of course Moor Park itself.
"Any more fares please?" the small lady bus conductor called out in her broad Northern Irish accent as she passed along the centre aisle of the red London Routemaster bus while it meandered its way from traffic light to traffic light along the busy thoroughfare of Oxford Street.
Whilst most of her passengers thoughts where on their journey plans or shopping or looking out through the comparatively small windows of the vehicle at the bustling street scene outside, two of those under her care, seated together across the nearside rear lower deck bench seat that was positioned lengthways over the rear wheel arch, had only each other on their minds.
The little Irish bus conductor did not need to see their passes or collect any fares, the uniforms that the couple where wearing signified their status in the world as officers of the Department of National Security & Civil Defence, the organisation responsible for policing the Untied Kingdom.
Specifically the epaulette insignia signalled this couple as no ordinary patrol officers either but the LT01 of the man and the LT02 of the lady meant that the humble bus conductor had a couple of major celebrities on her bus that late spring afternoon in the form of the Commanding Officer of the London Capital Transport Division, commonly known simply as 'The Commander' even though he was now a Divisional Superintendent, and with him his deputy in the Division, Deputy Divisional Superintendent Tracy Caverner.
Today was a very special day for them and by the same token a very ordinary one as well for despite the fact they had finally got married not two hours earlier, they where back on duty again as a shortage of senior duty officers that day meant a very short honeymoon spent eating chocolate acquired from a Underground station vending machine in their office half an hour earlier.
"Tottenham Court Road!" the bus conductor called out which became the cue for a flurry of activity as passengers alighted and boarded through the open rear platform of the bus despite the fact it was still moving albeit slowly across the main crossroads and still some distance from the next official bus stop.
"So where are we going to have the honeymoon then?" Tracy asked her new husband who now seemed a little distracted as he looked out of the rear bulkhead window of the bus at something that had caught his attention behind them.
"Berkeley Square" he muttered in a slightly incoherent reply.
Tracy quickly realised that something was distracting him and he had quite clearly not heard the question properly. "And there was me thinking Pentonville Road" she replied casually with a sarcastic grin.
"Not likely, its not on Route 8" he replied, his attention still away on what ever it was that had caught his ever watchful eye.
Tracy was used to surreal moments like this, despite or perhaps because of the serious and highly important nature of their jobs, moments like these where not uncommon especially with their serious dedication to the service.
"HMV and Burger King!" the conductor called from the rear platform so that her voice could also be heard up the stairs on the upper deck as well.
The thought of the ready availability of fast food unusually went unregistered by the Commander whose dreadful chip dominated diet, despite Tracy's best efforts to persuade him otherwise, was still a primary feature of his character.
"Blimey, it must be serious" she remarked seeing his lack of reaction to the conductor's announcement.
The Commander swung back round to face his wife. "Sorry" he responded "but something's bugging me".
"Oh welcome back!" Tracy remarked. "I was away?"
"Well we just passed a burger joint and you didn't flinch once so something was definitely on your mind".
"Behind the bus behind us" the Commander explained leaning back slightly so Tracy could see over his shoulder at whatever it was that had caught his attention. "Black four door Vauxhall saloon, two suited gentlemen in the front seat trying not to attract any attention".
With the bus now stationary at the traffic lights that guarded the complicated crossroads where Oxford Street met Regent Street, the bus behind pulled out and alongside revealing the car that had attracted the Commander's attention.
"Could be just out for a drive" Tracy commented.
"Something doesn't feel right though" he added "they have been following us since they pulled out of the Bloomsbury Court lay-by back there".
"Oxford Circus!" the Conductor cut in "Alight here for Victoria, Bakerloo and Central lines and Regent Street!"
"You could have a point" Tracy observed as she noticed the car went over Oxford Circus and continued to follow the bus to the route 8 stop whereupon it discreetly drew in to the side of the road despite the opportunity being there to overtake the bus and carry on.
The Commander discreetly picked up the radio from his belt clip and with his back turned to the rear of the bus, contacted the divisional control room back at their head office in Holborn.
Lieutenant Commander Simon Fuller was the number three officer in the chain of command within the Transport Division and that afternoon was where he could most commonly be found, the duty controllers desk in the large control room at the Holborn office.
He was still feeling a little tired having rushed both to and from the Commander's and Tracy's wedding a couple of hours earlier, he too was affected by a general shortage of duty officers that day and had been on duty since 7 am.
It was with a little resigned reluctance that he reached across the desk to pick up the radio headphones when he heard the Commander call in.
"Control from Lima Tango Zero One, receiving over."
If it had been anyone else then Fuller would have let one of the despatch officer's deal with it but as it was the Commander, he decided it ought to be he who dealt with it.
"Control receiving over, what's up Chief?"
"We are on a number 8 bus about half way between Oxford Circus and New Bond Street" the Commander explained "and we seem to have picked up an uninvited guest on our tail".
"That wouldn't happen to be a black Vauxhall Omega about fifty yards behind Routemaster RML2706 would it per chance?" Fuller enquired as he called up and found the appropriate CCTV camera view on his console.
The Commander was suitably impressed at Fuller's expertise but to him it was second nature in his other job as the Division's computer expert.
"Run the number through the computer will you?" the Commander asked.
"Will do" by which time Fuller was already running the registration number of the suspicious car through the system. He raised a surprised eyebrow however at the result which he received and immediately passed it on to his superior.
"Err boss" he announced "that number has a black flag on it". "A what?" Tracy asked.
"Black flag" the Commander explained, "That means it belongs to someone who doesn't want us knowing who they are".
"Hang on a second, I'll consult my special files" Fuller added. "What do you reckon, MI5 or Special Branch?" Tracy asked.