As well announcing a huge £1.5bn investment at Solihull in building new aluminium cars, what was critical about last week's announcement by JLR was that effectively it was a statement of intent. A range of new all-aluminium models will spearhead a major expansion of the Jaguar brand and contribute towards JLR's growth over the next few years.

Underpinning the models will be a brand new scalable aluminium architecture - known at JLR as iQ[AI]. This will underpin a range of models, starting in 2015 with the much-needed 'medium sized sport sedan'; in other words the new baby-Jag which will go head-to-head with BMW's best-selling 3 Series.

A Jaguar 'Sports Crossover' (or SUV to you and me) based on the same architecture will follow. Both models are critical to boosting Jaguar - and JLR - volumes, and have been seen as key gaps in the brand's product offerings so far.

It's not before time; as I've noted before, while Range Rover and Land Rover brands have roared ahead of late, Jaguar has underperformed, thanks in large part to some major gaps in its product range.

Jaguar's present range offers two sports cars and two executive saloons, and these are in slower growth segments of the premium market. Sure, the beautiful new F-Type has just filled one gap, namely for a two-seater sports car that harks back to exciting E-Type times. And the XF Sportsbrake now offers an estate Jag for the first time since the X-Type (a much undervalued car) was discontinued back in 2009.

But there are still some glaring gaps in the Jaguar line up; notably in the form on an entry-level saloon to fight the BMW 3 -Series and Merc C-Class, and a crossover Jag that uses Range Rover's advanced 4-wheel drive technology to target the rapidly expanding SUV market (it's no surprise that VW has just announced an extension of its SUV platform sharing strategy to include Bentley; Lamborghini is likely to be next).

The Porsche Cayenne SUV (based on the same platform PL71 platform as the VW Touareg and the Audi Q7) was launched over a decade ago, and makes up over a half of Porsche's sales now. Meanwhile, the smaller premium sector is doing well, even in moribund Europe, as buyers are prepared to spend more on a premium car like the BMW 1 and 3 series.

The new Jaguar models are also seen as key for China, the firm's biggest market. Here the Evoque and the Freelander are JLR's current best sellers. But with the SUV market there set to treble by 2020, Jaguar itself needs an SUV presence.

While the C-X17 Crossover is still a design concept, prototypes have already been seen on roads, suggesting that Jaguar will indeed enter this segment for the first time, and as early as 2016.

And as Jaguar's brilliant design director Ian Callum pointed out to Autocar magazine recently, "we were caught out with the C-XF concept and underdelivered; we now need to show things we know we can deliver." In other words, a Jaguar crossover is coming, and is aimed at the Audi Q5 and BMW X3. It's no surprise. This the biggest and most rapidly growing segment for premium SUVs.

Looking at the video of the C-X17, it's clear that design cues from a range of Jaguar models are evident. The front echoes the XJ with its large grille and slim headlights (that set-back grille in turn echoes earlier classic Jags), while elements of the F-type sports car (in turn echoing the famous E-type) can be seen at the back in the flat tail lights and rear haunches. It's unmistakenly a Jag, even if it's an SUV.

Just who is Jaguar aiming at with this SUV? As Callum notes, "there is an entire generation of 15 to 25-year-olds that doesn't care about sports cars or saloons... they aspire to own an SUV - especially in China" Callum added that "the tipping point came when we were doing the XF... I've always resisted this type of car, but we sent a research team around the world, and it found this is what the world wants."

Meanwhile, the much-needed new baby-Jag will be the first to be powered by a range of new four-cylinder turbocharged petrol and diesel engines. The SUV and some of the new Land Rovers and Range Rovers will follow suit.

These more fuel efficient engines will be made at the new £355million i54 engine plant near Wolverhampton. Currently under construction, the plant is due to open in 2015, with its first engines going into the new Jaguar model which will take on the BMW 3-series.

The new architecture will underpin a range of new models, thereby helping Jaguar to get development costs down. That range of cars will include fuel-efficient diesels emitting less than 100g/km of CO2 (critical for the firm in meeting new emissions requirements), as well as fast sports models using the F-Type's supercharged petrol V6 which can top 186mph (and which featured in the C-X17 on display at Franfurt last week).

All of this is needed as JLR's recent growth has been very much driven by Land Rover and Range Rover brands and Jaguar is effectively an under-exploited brand. Over 80% of JLR's annual sales currently come from the Land Rover/Range Rover brands.

So 'rebooting' Jaguar, developing and building its own engines, and cutting emissions are the key challenges the firm faces as the amazing turn around for the firm continues.

The real hope is that JLR's recent success can become sustainable growth over the medium to long-term - for that Jaguar needs to play a much bigger role in helping the firm to grow.

* Professor David Bailey works at Coventry University Business School