Fish and chips are hailed as Britain's national dish and one that is steeped in tradition. But there are many lesser-known tricks of the trade that only those who have worked in it will know.

While other fast food joints like McDonald's and KFC entice customers with "secret" menu items, the iconic fish and chip trade is a little different.

The team at Poppies, an iconic chain of London chippies, has divulged the best-kept secrets of the industry. Poppies takes its name from Pat ‘Pops’ Newland who founded the chain after entering the fish and chip business at age 11, when he got a job on the Roman Road cutting up The Daily Mirror newspaper to wrap fish and chips in for takeaway.

Now the chain sells the great British classic in all its glory at four London locations; Soho, Spitalfields, Camden and Notting Hill.

But even with its glorious offering of delicious, fresh dishes, there's one item the Poppies team wouldn't be caught ordering.

They told Express.co.uk: "It would have to be jellied eels. They've been a popular dish since the 18th century and lots of our customers love them but if you're new to the dish it can be quite a demanding bite!

"We serve them in the traditional way which is cold having been chopped, boiled and coated in a spiced stock that sets around the pieces of eel forming a jelly."

As for best-sellers that the team and their customers are most partial to, it has to be cod and chips. They're ordered "all day long", said the Poppies team, who revealed that a staggering 70 percent of Londoners favour cod over other types of fish.

And it's no wonder considering the unique offering Poppies restaurants - fresh. not frozen fish.

The Poppies team divulged: "A lot of fish and chip shops use frozen fish fillets which I don't think many people realise.

"The fillets come from far away and can be frozen a long time before they end up on your plate. It's one of the main points of difference at Poppies.

"We only ever use fresh fish, caught sustainably and responsibly from the waters around Peterhead in Scotland. Every day we receive the fresh catch, our skilled fishmongers fillet and prepare the portions and then they are coated in batter and cooked to order for our customers."

No order of fish and chips is complete without a flavoursome side, and at Poppies, mushy peas are the best-seller.

The team revealed: "Curry sauce trumps gravy amongst our customers but the number one side is always mushy peas."

These delicious sides accompany a staggering 13 tons of potatoes that are peeled in Poppies kitchens each week to make the 40,000 portions of chips that are bought each week.

While everyone has their favourite chippy, Poppies serves an impressive 10,000 plus Londoners who indulge on a portion of fish and chips each week.