How to start a thriller

From years of experience it's almost impossible to please literary agents or publishers when you send them an idea for a thriller or the first few chapters. "Oh," they say, "we like the idea but I'm afraid there's no commercial value in such a book" (ie we won't make enough money), or "you need to start with a big bang, something so arresting that it will grip the reader from the moment they open the book". Ok I go along with that, although I've read tons of brilliant books, thriller and others, where there's no big bang in the first chapter. Or "thank you for you letter/email and your first three chapters but I'm afraid we have our own A List of authors and really don't have time to consider adding to our list." Well,that's daft, how else are they going to find new authors? Or "I'm afraid there's too much humour in this book. A thriller has to be a thriller, you can't mix styles, there's no commercial market for a funny thriller." No comment on that, other than to say, how about a new genre - a comical thriller?!! So, I have started a thriller and the first few pages go like this, see below. If anyone fancies giving their opinions on the work so far, do please feel free. Just a short comment at the end would be much appreciated. "The motor bike rider, dressed in black leather and dark grey helmet, waited round the corner on a single yellow line. He was perfectly still. The 650cc BMW engine was running. Pedestrians walked past him without looking. Behind him, traffic on the Embankment heading for Parliament Square was building up. It was 8.12am, Friday. Five minutes went by. The rider glanced into a large wing mirror on the right handle and spotted a Jaguar saloon turning from the Embankment into the road. He checked the registration and tightened his lips. As the Jaguar passed him, he turned his head slightly. One passenger, sitting on the right-hand side at the back, reading The Times. The passenger was female, smartly dressed. The rider moved off slowly and followed as the Jaguar turned left. The street was surprisingly empty of people. One woman with a dog was walking on the opposite pavement. No other cars. The Jaguar slowed right down behind a large building, the driver apparently waiting for garage doors to slide back. As the Jaguar driver began to turn left down the slope into the underground car park at Thames House, headquarters of MI5, the motor bike rider accelerated. The woman in the back of the car briefly lifted her eyes from the newspaper and saw the rapidly approaching motorbike. Her mouth opened. But at that moment, the black leather rider, now armed with a Glock 19 pistol in his right hand, fired four 50-calibre rounds, each travelling towards the intended target at 1,400ft per second. The first two were blunted by the bullet-proof glass, transforming the window into a kaleidoscope of shattered lines and circles. The woman’s face disappeared from view behind the rippling mess of glass. But the next two rounds penetrated the smashed window with explosive force. The Jaguar driver slammed his foot on the accelerator, and the garage doors swung down behind him. As the bike rider sped away, he heard a screech of brakes and a crash from behind the garage doors. Three seconds had passed. The rider turned left at the end and then right, swerving recklessly across the Embankment traffic lanes, heading west. He drove through red lights and crossed Vauxhall Bridge, now travelling at 60mph. Staff in offices on the south side of the bridge, overlooking the Thames at 85 Vauxhall Cross, home of MI5’s sister agency, MI6, were too busy on their computers to be aware of the speeding motorbike. The rider went through red lights for a second time and continued driving fast. He heard the first police siren but it wasn’t close. The woman passenger in the government Jaguar lay on the back seat, her face and hair covered in blood. The driver was badly concussed and his right leg was broken. He couldn’t turn his head to see whether his passenger was alive. The car was filled with smoke. A tumult of MI5 security guards came rushing into the garage, guns raised. They wrenched open the front and passenger doors. But before handling the driver and passenger, they checked everywhere inside the car, looking for any sign of a device. MI5’s emergency alert alarm pulsated throughout the building."