A significant challenge now at the door of M&S is how to explain its worst underlying quarterly sales performance for three and a half years, which I reported on last week.

M&S CEO, Marc Bolland, has put the blame at the door of poor weather conditions, together with stock shortages in bestselling lines.

Of course, this will explain some of the M&S figures. But it is tempting to reach for cursory explanations when there may be more fundamental issues to examine.

One of the challenges I see that M&S faces is inconsistency. Inconsistency between stores, between shoppers’ in-store experiences, and between its products. Good customer service at some stores, occasionally poor at others. Two billion pounds spent on revamping some stores, whilst others look shabby. Good quality fabrics on some products, synthetic fabrics on others.

This inconsistency is problematic for a brand for two reasons. Firstly, people become unclear about what the brand stands for. Secondly, people find that the brand becomes unreliable. Take the example of a female shopper interviewed by the FT this week at M&S Kensington High Street. Clutching an armful of M&S clothes in the sale, she says has been put off by the poor quality fabrics and buys her clothes elsewhere. Once a loyal M&S customer, she now only shops at the department store during its sales. “It’s such a hotchpotch – you sometimes find something,” she says. “This is one of the better stores”.

Inconsistency and an unclear brand isn’t something its rival John Lewis suffers from. Its performance is shining, it has successfully revamped its fashion wear, and it continues to innovate, having just teamed up with designer Alison Temperley and launched a new home brand, ‘House’.

One of the implications of all this is that one of the best loved retailers on the high street is at risk of being taken over. The M&S share price has fallen 13% over the last year. If it continues to fall, then it is likely to attract the attention of private equity groups or a sovereign wealth funds.