Are there abundant prawns in your sandwich? The ultimate aftertaste test

Supermarkets have become our go-to sandwich suppliers, but when Channel 5’s Shop Smart: Save Money put some of our favourites to the test, nearly half contained less than the advertised filling. The amount of stuffing also varies wildly, with Roy Keane’s old bete noire, the prawn sandwich, the most inconsistent – a Boots version contains 22% of prawns compared with M&S’s 41%. And what about the taste? Which are the king prawns of the sandwich world and which are the shrimps?

Waitrose, prawn mayo, £2.40

Despite its foodie rep, Waitrose’s sandwiches are often terrible. Its prawn mayo is good, however, with 38% prawns, bound in a creamy mayo on fresh oatmeal bread. And the prawns are certified sustainable by the Marine Stewardship Council (MSC). 3.5/5

Spar, handmade prawn mayonnaise, £3

Despite being the most expensive of the lot, you may struggle to finish this drearily bland sandwich. The prawns are there (39%), but rather than seafood, the dominant flavour is the flat, eggy one of poor-quality mayonnaise. 1/5

Co-op, prawn mayo, £2.35

More MSC-approved prawns, which make up 40% of the sandwich. They are evenly distributed – none of that supermarket “middle-diddle” here, where they pack the fillings in the centre to make it look attractive. But, still, it fails to impress. The lingering flavour is not prawns, but the darker malted bread that is used. Most use a lighter oatmeal. 1/5

M&S, prawn mayonnaise, £2.50

While this is packed with fatter prawns (41% of the whole), the coverage peters out at the sandwich’s edges and the flavour never gets going. The prawns are woolly little critters, a footnote to the bullying top-note of black pepper. 2/5

Sainsbury’s, On the Go prawn mayonnaise, £2.25

Never mind store-to-store variation, this sandwich varies in its two halves: one thinly smeared, the other packed with prawns that constitute a healthy 40% of the filling overall. These MSC-stamped prawns look small but are surprisingly meaty and, if lacking sweetness, pack a decent flavour. 3/5