To some observers, the absence of two of the UK’s biggest law firms from a place around the deal table at one of the standout takeovers of the year so far will have raised eyebrows.

Despite winning mandates on previous transactions involving the main players in the deal, neither Clifford Chance nor Slaughter and May were involved when US drugs giant Walgreens revealed it was to complete its takeover of UK pharmacy chain Alliance Boots earlier this month.