The magic has well and truly evaporated from the retail Camelot created at Marks & Spencer by Sir Stuart Rose.

Little more than four years after his coronation, Rose must consider seriously the possibility of being dethroned. Pali International analyst Nick Bubb believes there’s a 40 per cent chance that Rose could be forced to step down or resign “in due course”.

It’s been a terrible year for Rose; he’s rarely been off the battlefield. The hostilities started after M&S’s Christmas trading disappointed, then the row over corporate governance flared up and this week’s shocking sales update has prompted more misgivings about Rose’s role.

Things may get rowdy at next week’s AGM, but the big question – whether sparked by Rose’s elevation to executive chairman or by the latest trading numbers – remains: who could do a better job?

During the call following Wednesday’s announcement, Rose highlighted his experience of coping with downturns. Unlike a substantial number of today’s retail directors, he has been through slowdowns before, including some of the worst. He knows how to trade through hard times.

He made a convincing case that M&S remains a strong company in a weak market, while acknowledging that some of the company’s problems were self-inflicted.

He said that was true for about 40 per cent of the retailer’s present difficulties in food and he has dispensed with the services of food boss Steve Esom. The unfortunate Esom has only been at M&S for a year and, just a few months ago, was promoted. He was seen as a potential successor to Rose. Esom’s failure also looks like a failure on the part of Rose, to pick the talent that really could take the reins when he moves on.

Which takes us back to the question of who could be M&S’s next leader. Not all of the internal candidates may want the role and not all will be suited to it. Now is certainly not the time to try and unseat Rose, because there is no obvious replacement. Although there may be arguments about the extent to which M&S is a victim of the downturn or management failure, there is no doubt that the downturn has taken a toll. Rose remains M&S’s once and future king, but he could do with a few more Merlins at his side.

Talking of corporate governance, its importance was highlighted this week at a business at the other end of the scale from M&S – variety store group Instore. One of Instore’s shareholders, Seaham Investments, is trying to take control of the business in a deal that values it at£11.4 million. Another leading shareholder, Tradegro, has given an irrevocable undertaking to sell its stake.

Independent view is vital

But Instore’s two independent non-executive directors believe the retailer is being undervalued and have urged other shareholders to take no action on Seaham’s offer. It’s a reminder of the valuable role undertaken by independent non-execs. As gossip does the rounds that M&S’s decimated valuation may flush out bid interest, investors will want to be sure that its non-execs are up to their jobs as Sir Stuart Rose wields power as executive chairman.