Glenryck is more well known for mackerel, but a couple of years ago I discovered that their tuna is very good too; at least as good if not better than the more popular brands, but it is very hard to find in shops. This appears to be the normal selling price in Morrison's as there are no brightly coloured shelf labels.
No 'buy one (at double price) get one free'
No 'price crunches'
No need to buy 240 tins to get the right price