To Haggle Or Not To Haggle?

I have to confess that I attempt to get a discount off some items these days. Not everything. I do most shopping online nowadays. The Barbour cap I got last week was bought online.

That said, there still seem to be stores where bargaining, or haggling is, shall we say, discouraged. To take one example, I'd be slightly reluctant to haggle at Turnbull & Asser where I get some of my shirts. I imagine it would be worth a try - nothing lost, nothing gained and all that.

I wonder how you'd go about haggling at Marks and Spencer? Would you look for a blemish on something and exploit that, for instance? How many people haggle at Marks & Sparks, I wonder?