Everyone likes adding on a few extras when they order their new car, that’s half the fun. The question is, where do you stop? If you are buying a new 7-series direct from BMW, pay another £600 and you get a phone in the back – a good idea because in a car like this, you’re going to spend a lot of time being driven.

You can drop another £500 and add a little more joy to your ride with the oscillating seat base function. Velour floor mats are really a personal choice and it’s a call I think you should leave to your better half and their interior designer. But, if you want to go the whole distance, there are some things you can’t find on BMW’s website or in the main salon at the Geneva motor show.

Get on the phone, go through a few checks and you can order a package that includes a boot too small to carry a set of golf clubs (caused by 6 inches of steel encasing the passenger cabin and shielding the function-critical electrics) a windscreen (so heavy you’d never be able to kick it out in an emergency) fitted with a ring of explosive charges around the edge to hurl it across the road. You can also pimp your ride with glass that’s 4 times as thick as the hardback edition of the London A-Z and doors so heavy they’ll throw your arm across the road the first time you open one. You can pick out some extra wide, double-chamber, Kevlar–lined, run-flat tyres and a neat little intercom system that every urban runaround truly shouldn’t be without which mounts speakers and mikes in the wing-mirrors and allow you to communicate with the outside world without stepping into it. There’s undercar shielding against IEDs and a neat little switch covered by a Perspex hood marked ‘Fire’ which disappointingly doesn’t return fire at the baddies but does spray a torrent of foam under the hood to put out a grenade fire and allows you to drive on to your meeting.

All this will set you back around another £130,000 and if you pass a few more tests, the least of which is whether you can afford it, your car turns up with a variety of sirens and flashing lights, your own oxygen supply and an interior roof-mounted lockable weapons compartment and yes, small openable quarter lights from which you can return fire upon the baddies.

This is the car BMW Specialist Operations, out of Munich, lent me for a few days and, from the outside, it takes a trained eye to notice any differences: it runs the same height on the suspension, none of the pillars or posts seem thicker. There is a slight giveaway in the refraction of the glass but that’s about it.

There are one or two other high-end manufacturers out there armouring their cars: of course there are. If you’re spending £269,500 on a new Rolls Royce Phantom, you can probably specify the parentage of the seat leather, so a few add-ons like a humidor or drinks set won’t raise an eyebrow. Similarly with the Maybach; there probably aren’t many discreet introverts ordering one, so don’t be embarrassed to ask for a few extras.

The BMW, however, is the only one that has its armoured features incorporated on the production line and once you’ve driven in it, you start to see the world differently. We copped a ride across London to an advertising event. A bit of fun really: turn up for a black-tie dinner with a bunch of long-haired crayon-pushers in a Presidential-protection vehicle. But a long traffic jam over Westminster Bridge threatened to make us late and Andrew our driver is applying the first rule of security, which is to be discreet - however much we beg him to open the window, slam the magnetic base of the blue light onto the roof and clear us goddamn space. Just as well really.

When we pull round the corner, we see the reason for the hold up. At 7pm on a May evening in York Road, the officers of CO19, the Metropolitan Police’s specialist firearms unit, appear to be cracking open a building. This is no dog and pony show. There’s a ring of police with fingers on semi-automatics and faces like death, standing on the pavement facing outward. A line of immigrant workers are being chivvied out of the fire exit door of some non-descript cement building. A white transit van is pulled up on the pavement; one of theirs with 500 lbs of homemade in the back? Or one of ours with the surveillance equipment for this job? Who can say what’s going on in London these days? One thing we know for sure is that if it does all go off, we’ll be fine. Our car has B7 protection: this means the bodywork will resist - only an idiot or a fraud ever claims complete bullet-proof abilities - armour-piercing rounds fired from an AK47 and a grenade attack (B6 standard is one step down and is designed to resist normal AK47 rounds). And if fire does get under the car, we can damp it with the fire extinguishers and drive on, we can run on those shot out tyres and the personal oxygen supply will engage if the sensors pick up unusually toxic or high particulate content in the air coming in.

But hold on, let’s wind it back a bit there. ‘Who can say what’s going on in London these days?’