Sebastian Vettel dominated the Indian Grand Prix to make it four wins in a row and the question on everyone's lips in Formula 1 is: how have his Red Bull team turned around their performance so dramatically?

They have been there or thereabouts all year, always competing close to the front, but Vettel's last victory before his current run was in Bahrain in April, the fourth race of the season.

Now, however, the topsy-turvy form of the first half of the season that saw seven winners in seven races has been replaced by total Red Bull domination.

I'm going to try to explain how they have done it.

Red Bull's recent form is founded on a package of upgrades that started at the Singapore Grand Prix and has been refined ever since.

The effect has been to take a car that had good race pace but which the drivers were struggling to consistently qualify at the front and put it unfailingly at the front of the grid. From there Vettel can control the race.

Much of the secret lies at the back of the car.

quote Red Bull's strategy is only guaranteed to work if they qualify at the front and then break free in the opening two laps before DRS use is allowed. If it does not qualify at the front - or if Vettel makes an error in the first two laps and drops back - he would have a problem

There, chief technical officer Adrian Newey has found a way to recover more of the rear downforce that was lost through the banning of exhaust-blown diffusers at the end of last season than anyone else.

Exhaust-blown diffusers, and Red Bull's mastery of that technology, was what helped Vettel to his domination in 2011. The huge boost in rear downforce required a counter-intuitive driving style.

Normally when a car oversteers, a driver corrects it by lifting off the throttle and/or applying opposite lock. But the extra rear downforce created by the exhausts blowing along the rear floor and 'sealing' the gap between it and the rear tyres meant that by applying extra power when the car slid, it would grip again.

That downforce was lost with the banning of exhaust-blown diffusers. But Red Bull, under chief technical officer Adrian Newey, have been working away all year at trying to get as much of it back as possible, to allow them to run their car set-up - and their races - as they were in 2011.

So have all the other teams of course but, finally, Red Bull has unlocked the door. The new design is nowhere near as effective as an exhaust-blown diffuser but it is closer to it than anyone else has managed.

A revision of the rear bodywork has changed the direction of the exhaust gases and the way they interact with the rear aerodynamics.

The gases are guided down channels inside the rear wheels, sealing the gap between the tyres and the diffuser sides.

That means the diffuser creates higher levels of downforce at the high rear ride-heights and large degrees of car rake (front down, rear up) that Newey likes to use.

The benefit of running a car with high rake is that at low speed the diffuser, or rear underfloor of the car, gives more downforce - as long as it can be made to work properly.

But there are difficulties to be resolved too, and it is doing so that has put Red Bull in their current position.

Firstly, at high ride heights the diffuser leaks more air, which reduces downforce. So it only produces more downforce than a car with less rake if there is a mechanism to stop that happening.

In 2011, Red Bull did that with the exhaust-blown diffuser, by pumping the exhaust gases into the gap between the tyre and the diffuser. This works the aerodynamic devices on the rear brake ducts much harder, and they in turn 'seal' the diffuser - stopping air spilling around its edges.

The second problem is that when the car goes closer to the ground, as it does at higher speed with downforce acting upon it, a diffuser that works at high ride-height will stall earlier because the airflow cannot stay attached as the air pressure under the car decreases.

But Red Bull now have a way to stop this happening.

Indian GP top 10 1 Sebastian Vettel - Red Bull 1:31:10.744 2 Fernando Alonso - Ferrari +00:09.437 3 Mark Webber - Red Bull +00:13.217 4 Lewis Hamilton - McLaren +00:13.909 5 Jenson Button - McLaren +00:26.266 6 Felipe Massa - Ferrari +00:44.674 7 Kimi Raikkonen - Lotus +00:45.227 8 Nico Hulkenberg - Force India +00:54.998 9 Romain Grosjean - Lotus +00:56.103 10 Bruno Senna - Williams +01:14.975

They have two ducts - letterbox-shaped horizontal holes - in the transition between the two levels of the floor of the car, the 'step plane' and the 'reference plane', which let air through into the diffuser. This aspect is similar in some ways to the double diffusers of 2009.

These ducts are fed by air coming through the coke-bottle shape external-link between the rear wheels, and when the low pressure under the car gets to a certain level it sucks in air and keeps the airflow attached.

So that gives the car better speed in both low-speed and quicker corners. But the system is made even more effective by Red Bull's 'double DRS system' on the rear wing external-link , which no-one else has.

That interacts with the airflow from the diffuser so that on the straight, when they don't want that extra downforce under the car, the airflow across the lower rear wing and the diffuser is changed so that the downforce is reduced and the car goes faster in a straight line.

So the whole back end of the car is a very clever application of two technologies that have been banned but in a new way that is legal under the current rules. It's less effective than a double diffuser or an exhaust-blown diffuser, but it's a similar principle.

Hence the step-change in Red Bull's performance since they introduced it at Singapore and then developed it further into Japan and through Korea and India.

There is, though, one potential flaw in Red Bull's entire approach.

Because in the race the 'double DRS' system can only be used when a driver is within a second of a car in front in a dedicated zone, the Red Bull is potentially vulnerable in the race because of its lack of straight-line speed.

So the strategy is only guaranteed to work if they qualify at the front and then break free in the opening two laps before DRS use is allowed.

In a car that good, and with Vettel at the wheel, that can be taken pretty much as a given.

But if it does not qualify at the front - or if Vettel makes an error in the first two laps and drops back - he would have a problem.

The way he and Red Bull are operating at the moment, however, the problem is all their rivals'.