It pains me to criticise a brand I have myself contributed to, if only briefly. But unless I am much mistaken, the concept of being taken “hook, line and sinker”, refers to swallowing the bait. As in being conned, or falling for some kind of trick or lie. Are we then to assume that Marks and Spencer have fallen for a policy which they know now to be a trick, a fiction, a fraud? And are choosing to stick with it?
It’s the worst kind of copywriting. An attempt at clever word play that pays no attention to context or meaning. Although I suppose believing in something is quite a lot different to actually doing something about it.