Insane Mode. We knew the Tesla Model S P85D was going to be exciting after seeing the word Insane as an option, but we didn't know the half of it. We went up in a stunt plane recently and pulled 5G. The P85D was more exciting.

Writing this with shaky hands as the adrenaline courses through the system (from hurtling along from 0-60mph in 3.1 seconds), the fact the P85D is all-wheel drive and uses dual electric motors, means the torque of 691bhp is delivered all at once. It's like being on a roller coaster but really, really, comfortable. We're not the first to be impressed with Insane Mode - just check out these reactions.

So how has Tesla come to this point and is the Model S P85D worth the £79,900 starting price?

The story so far

Tesla is steadily making inroads into the UK with its electric cars. First there was the Roadster, then the Model S 85, 85D and 70D and now we've got the all-wheel drive Model S P85D.

The P85D isn't the first Tesla to get all-wheel drive as the Model S 85 now has a dual-motor big brother in the 85D, yup that's what the D in the name stands for. There's also a cheaper base Model S 70D with shorter range than the others.

The all-wheel drive 85D models are more range efficient, handle better and are faster. But the P85D is the fastest of the lot and is now available to order in the UK for delivery around October 2015.

Power without losing luxury

The only noticeable external difference between the new Model S P85D and its older siblings is coloured Bremmo brake calipers and a small rear spoiler.

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The interior of the Model S P85D doesn't scrimp on luxury with a suede finish to the top dash and a carbon fibre front on our test unit. The sports seats are deeper and more bucket-like than the other models, which were needed to stop you rolling out of the seat when throwing this animal around.

It feels luxurious, like the inside of a Land Rover, only with a more minimalist look, as most controls are found on the wheel or in that 17-inch central touchscreen. Even the rear offers three full adult seats owing to the car's width. Behind them is enough storage to extend the car to a seven seater if you opt to pay extra for the two rear-facing seats that fit in all that boot space.

Driving modes and smart extras

When pulling away the Sport Mode is fast, but not much faster than the Model S 85 rear-wheel drive model. It's when you tap on Insane Mode that the ride changes. This throws you back in your seat and the extra front motor, we imagine, sounds like going into hyperspace. Very satisfying stuff.

Cornering offers more than enough grip and with that all-wheel drive system intelligently distributing power you'd have a real job trying to kick the back end out. We tried and failed. While we mainly used Sport Mode for the steering there's also a comfortable setting that makes the wheel super light, ideal for driving about town.

It's the little things that make a difference though. The door handles that slide out of the car when you approach, the multiple profiles to adapt to up to 10 drivers' preferences at a touch, opening the sunroof by sliding the touchscreen to a certain percentage, or the ability to learn your calendar so the car is charged, warmed and ready for journeys you may not have even remembered the night before. It'll even check the traffic and let you know if you need to set off early.

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The key fob is fun too. It's car shaped. Double tap the boot to open and close, with the same for the front storage area, or the middle to lock and unlock. It auto opens as you approach but we didn't have the guts to walk away and trust it to lock itself, although this does work. Our only complaint here is the double tap is a bit tough with no discernable click. We want something a little more tactile.

One very nice option is the ability to change suspension ride height. We had it set on lowest, for performance, but when on a road with bumps, you can hit the on-screen button and it changes to offer greater clearance height. But it gets better. This is GPS smart so if you have a particularly steep drive at home it'll learn that and automatically change the ride height when you arrive there. It'll even link to your electric garage door so all you have to do is drive right in.

If you're giving the car to a valet or cleaner you can set it in Valet Mode. This pin code locks the boot and hides personal details, like address, as well as prohibiting access to the internet browser. Security remains apparent, even in your connected car.

Automated driving

While the Tesla Model S P85D can technically drive itself using Autopilot mode, laws need to be passed before that system is rolled out as a software update in the UK. For now you get lane assistance, so it won't steer for you, but will alert you if you stray off - which is common to many marques. But in the future this will steer to stay in lane and the use of an indicator will be all it takes to change lane.

There is also adaptive cruise control as an optional extra, to maintain a distance from the car in front without you touching the pedals. We were initially a bit nervous with a foot hovering over the brake with cruise set to a four car distance. After a while we reduced that to one car length and felt confident just using the wheel alone.

Self-parking is another option that means the car will be able to drive itself into parking spaces and even your garage at home. Well, not your UK garage as this is another legal issue that meant, in the model we drove at least, it doesn't work in the UK yet.

Infotainment controls

We'd heard complaints about that 17-inch touchscreen being awkward to control while driving. In our experience this wasn't a problem. Everything was large and clear enough to stab away at while driving along, and the interface was simple enough to learn quickly. What's key here is menus don't drill down, so you're always an icon tap away from what you want.

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There are dual controls on the steering wheel with menu screens in the head unit, if you prefer real buttons. This is a nice touch as you can leave the satnav and battery consumption in the head unit and have suspension or radio information on the main screen if needs be.

That 17-inch screen is backed by 3G connectivity, which comes with the car free for 4 years. It'll let you visit webpages and you can access connected services like internet radio.

Smartphones, be they Android or iPhone, can connect to the car via the Tesla app. This allows for control of the charging process, syncing of calendars and more. Any phone with Bluetooth should be able to connect directly to the car for playing music and taking calls over the car's speakers. This was easy to use thanks to a scrolling menu system in the head unit. It was also really clear thanks to the near silent operation of the car and the surround sound audio.

Range and long journeys

The Tesla Model S P85D has a spec-sheet range of 300 miles on a single charge. On top of that, for a long journey there are Superchargers and intelligent journey planning.

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There are now 22 Tesla Supercharger stations in the UK which can fast charge the car to 50 per cent in just 20 minutes. When you set your destination on the built-in Google Maps-powered satnav, the car will automatically plan it with any necessary stops at Tesla Superchargers.

It'll even give you stop times based on how long you'll need to charge for - so you can plan a lunch stop around a longer one for example.

Superchargers in the UK and Europe offer power at 120kW, meaning about 170 miles charge per half hour. We were told that if you're sharing a two-Supercharger bay the load is split, but if you have lower battery power it'll charge you faster than the other person.

By comparison Chademo faster chargers, which are all over the UK, work at 50kW which is about 85 miles per half hour.

The car has a realistic 253-mile range, so stopping regularly shouldn't be needed. The home charger is a 7kW adapter in the UK meaning you can get to full power overnight easily. The US has dual-chargers and higher power versions but right now the UK electricity infrastructure in older homes might not support that so Tesla is still testing ways to bring it to the entire UK.

First impressions

The Tesla Model S P85D is a supercar with the comfort of a high-end luxury sports car, plus it offers a futuristic feel no other car offers. It also feels more future-proof than the competition, and the price at just under £80,000 reflects that.

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Even when taking off the savings on petrol, road tax - and in the case of London, congestion charge - it's still expensive. Tesla offers finance but that'll mean paying £1,119 per month over 6 years.

Alternatively the Model S 85D offers a bit more range at a spec-sheet 310 miles and is a little slower at 0-60mph in 4.4 seconds but costs £63,580. Then there's the entry level Model S 70D for £55,000 but that means a spec sheet range of 275 miles, a slower-to-charge 70kWh battery and a 0-60mph time of 5.2 seconds.

The Tesla Model S P85D could be called future-proof. It's crammed with hardware and sensors that means it'll be a self-driving car one day, it is just a software update away and a hefty lump of legislation, of course. Software updates can offer free upgrades, like one which recently added horse power through an overnight update which Model S owners got for free.

But a car like the Tesla isn't really about saving money. This is the supercar for techheads. It's smart, connected, comfortable and offers the performance to put a smile on your face. It might have less appeal for petrolheads, but Tesla delivers in so many areas. At this price there are lots of rivals, from fossil powered to electric and everything inbetween. But in the UK a Tesla is still something of a rarity, it's something special and we feel the same sort of wonder for it as we do the BMW i8. 

The Tesla Model S P85D is a luxury and it's not only the speed and comfort that make it attractive, but because it feels like you're driving a car from the future. And one day, it might just be driving you.

READ: 11 best electric and hybrid supercars: Over 1,300hp from an electric? It's here