This is unashamedly not a recipe that I've adapted but a straight copy of Nigel Slater's simple surf and turf salad.
The term salad may seem a little strange in that there is no grass or leaves to excite the bitter taste buds and spoil the flavours of fish and meat. This is closer to a potato salad and the mackerel and bacon, in this case pancetta, go well with the rather complex dressing. It is complex in terms of flavours as opposed to production. The recipe is for streaky bacon but Nigel Slater suggests pancetta as a possible substitute, which I tried somewhat successfully.