Despite appearances, BMW’s relationship with the Mini brand is not quite as settled as it might be.

Although it clung onto Mini in the wake of the break-up of the Rover Group in 2000, there was a widespread fear within BMW that Mini could prove to be an expensive flop or a brief flash in the pan.

Read about and see the pictures of the 2011 Mini design concept here

Eight years on from launch, and after two generations of the new Mini family, that’s proved not to be the case. Even so, there are still plenty of worries about how BMW can grow the Mini brand so that it becomes self-sustaining.

Minis fundamental problem is that it is a relatively small operation (with sales of around 230,000 in a good year) using a stand-alone platform.

And it is not only BMW’s smallest volume platform, but the economies of scale are dwarfed by the BMW medium rear-drive platform which underpins about 800,000 new cars per year.

Even BMW’s big rear-drive platform (which underpins the 5-/7-series and X5/X6) accounts for sales of around 400,000 units per year.

Although it is thought that the average transaction price for a Mini was as much as £17,000, auto analysts suggest that figure is now sliding downwards.

In fact, one comprehensive analyst’s report last year suggested that while Mini probably made a small profit on individual model sales, the overall operation is probably making a loss.

The Mini is not only an expensive car to build, but investment in new models has been unrelenting. The 2006 Mini was virtually a new car and the stretched Clubman was an expensive car to put into production.

And now BMW is launching a second Mini platform – and second production line in Austria - which will underpin three more five-door models.

In truth, BMW probably needs to drive annual Mini sales up to 400,000 units and beyond. It needs to shift Mini away from a quirky niche brand into the mainstream.

But there are still signs that BMW has ensured the Mini division could be easily detached if the worst comes to the worst and the brand struggles to go mainstream.

A couple of years ago I was told that upcoming Mini Speedster was first conceived under the Triumph badge. The logic was that a Mini-Triumph division could support stand-alone dealerships and, if necessary, be sold off as a stand-alone business.

BMW has also seriously looked at platform sharing for future Mini models, something it would never countenance with BMW brand vehicles.

You also have to wonder about BMW’s decision to embark on a major project to build a family of two- and four-wheeler ‘megacity’ vehicles, powered by batteries and super-efficient petrol engines.

Logic would suggest that when the first Megacity model arrives in 2015, it should wear a Mini badge.

If it doesn’t, thoughts will immediately turn to Mini’s future and semi-detached status within the BMW family.