The glow of a new client win just might be fading over at Freshfields Bruckhaus Deringer today.

Unless you’ve been living on the moon, you cannot have failed to miss this morning’s lightning bolt that Slaughter and May is attempting to secure an injunction stopping Freshfields from acting for Philip Green on his much anticipated bid for Marks & Spencer (M&S).

Bear in mind that Green, billionaire owner of Bhs and Arcadia, hasn’t even tabled a bid yet.

And yet here is M&S, already the target of a prior takeover bid by Green, unleashing the might of Slaughters’ stable of corporate heavyweights.

No longer is this a case of the gloves coming off – this is full-blown warfare.

Remember that only a matter of days ago, M&S ruthlessly (or sensibly) replaced its chairman and chief executive. The retailer is proving that it is fully prepared to act decisively. Apparently, the old management had already instructed Slaughters to examine the Freshfields role, before Stuart Rose came in to replace chief executive Roger Holmes.

For Freshfields, the next few hours are critical. Slaughters may have taken a trip to the High Court, but as yet sources say an injunction has not been granted. But time is ticking away and, with the hearing starting at 2pm today, a decision is expected by close of business.

The issue is that Freshfields has in the past acted for M&S, and therefore the question is whether the firm had access to confidential information, therefore creating a conflict of interest.

True, in interviews conducted by The Lawyer with M&S head of legal Robert Ivens, he named Freshfields as one of the company’s preferred law firms, while The Times cites two examples of areas where Freshfields has been retained by M&S – one involving the contract with George Davies, the former Asda fashion guru who went on to join the retailer, and the other a litigation between M&S and supplier William Baird.

But there is no suggestion at all that Freshfields lawyers involved on previous transactions are now acting for Green.

Common practice is that if a law firm was concerned about conflicts, it would secure permission to act on a deal from the company – in this case M&S.

However, since the whole City is remaining resolutely tight-lipped about what has, and what is, going on concerning Freshfields, there is no way of knowing what has been happening behind the scenes.

One cannot help but wonder what Allen & Overy (A&O) makes of all this. A&O acted on Green’s last attempt to take over M&S and was also involved on the Arcadia deal. So where is it now?

And what happens if Slaughters secures the injunction? Will Freshfields garner its own fearsome reputation and fight it to the hilt? How will that wash with M&S shareholders?

Will Green return to A&O or will he attempt to instruct another firm altogether? Would he turn to Linklaters (apparently mooted as a choice)? And would Linklaters even want to take the instruction? Are other firms already acting for other potential bidders?

Whatever happens, the City is already hooked on what is set to become the fight of the year.