Zandra Rhodes and Betsey Johnson: Fashion grannies rock on

Two legendary doyennes of the fashion world have been making news this week -- and not just for their colourful fashions.

Today, Betsey Johnson announced a majority investment in her business from Boston's Castanea Partners. Some observers are questioning Castanea's logic for investing in a 30 year old brand whose namesake is already a grandmother and whose high-profile days are long over.  On the contrary, the business  has a solid own-retail network of 51 stores and a respectable $200m in sales. This could provide a great platform for further growth, as long as Castanea doesn't dilute the brand's famous quirky irreverence, which is what is most appealing to its loyal fans.

Earlier this week British fashion icon, Zandra Rhodes, garnered yet another high profile article highlighting the resurgence of interest in her designs around the world. While she doesn't have a business on the same scale as Johnson, she is still finding news ways of capturing value from over 3 decades in the industry, using her iconic colourful style as the basis for a series of licensing agreements with MAC (for makeup), Pologeorgis (for furs), and the Dash Partnership (for jewellery).

So, why are the fashion grannies on the rise?