This response is based on logic rather than knowledge - the eating habits of the local populace combined with the high overheads and low profit margins would make the running of a shop devoted entirely to fish and chips an uneconomical proposition - if there was a business opportunity there, someone would have exploited it by now.
It's because we want to keep the riff raff out and not have to look at people eating that sort of thing while we are sipping on our Cristal and nibbling our petit fours. Serioulsy though Andy is correct, rentals are high. Some of the cheaper-end bars (Bar Med, The City Litten, The Cross Keys etc) do it as a lunch and there used to be a F&C off Petticoat Lane.
Cheers guys but I was thinking more along the lines of an old law rather than economics ... I work in city and know there would be a huge demand for such a plaice in the square mile.
I think you also have to take into account the "traditional" trading days and times of fish and chip shops. Usually closed on Mondays and only open at lunchtime and evenings. Most of the city is deserted after 7ish so they would have to severely bump up their prices to make it pay from mainly lunchtime trade. As for being closed on Mondays thats to do with the fish not being available from Billingsgate over the weekend, so it wouldnt be "fresh fish" as such if it was kept all weekend. That leaves just 4 lunchtimes a week to make a living, I cant see it somehow !
Cheers Baz.... that actually makes a lot of sense. I'm still under the impression that there is another reason, a more traditional reason but thanks for your answers.