Heathrow is commonly known as Britain’s busiest and biggest airport and as such it is bursting with secrets, history and the kind of facts we all love to pour over.

While you bustle through it on your way to your holiday or business trip you probably aren’t aware of what goes on to keep it running smoothly and hidden areas behind the scenes which we never get access too.

Its size is enormous – but there is more to it than four terminals (no, there aren’t actually five), a control tower and two runways.

Here are ten astonishing facts you never knew about Heathrow Airport.

1. There is a virtual windowless control room away from the airfield if the tower is out of action

If the control tower at Heathrow Airport was out of action for whatever reason then there is virtual backup ready to take over and allow Heathrow to still operate up to 70 per cent of its flights and stay open.

But unlike the big tower overlooking the airfield, what is known as the Virtual Contingency Facility (VCF) is windowless and is in a secure site away from the airfield.

It is an exact replica of the visual control room at the top of the control tower at the airport and uses the same procedures, technology and radio communication put into action when controller can’t see aircraft from the tower, such as in thick fog.

2. Royalty and the rich and famous have their own VIP suites

The royal, rich and famous will use the VIP services

When she flew into the UK for the Royal wedding, the mother of the new Duchess of Sussex, Meghan Markle's mum Doria Ragland was reported to use one of Heathrow’s VIP Suites, reserved for the world’s most discerning customers, including Royalty and presidents.

There are two suites – the Royal Suite, which is reserved for royalty, and the Windsor Suite – but we don’t know where they are exactly.

Guests using the service pay at least £3,300 for the privilege. They can be picked up at home and when they arrive, the VIP Concierge team take care of their check-in and luggage, while the passenger relaxes in their private lounge, complete with TV, Wi-Fi, and food from Michelin Star Chef Jason Atherton. They can even make use of a personal shopper.

There’s no need for them to join the herds through main security gates either - they can go through all the security procedures within the suite and when their flight is ready they are driven in a private BMW 7 series car directly to the plane. Those arriving are met off the plane and whisked away by a luxury car to their private lounge.

3. Where is Terminal 1?

Has it actually occurred to you that, although you’ve probably seen signs to Terminal 2, 3, 4 and 5, there is actually no Terminal 1? Having been open in since 1968, Terminal 1 closed on June 29, 2015 after 47 years in service.

The last plane to leave was a British Airways flight to Hanover in Germany. Formally known as BEA, the airline was the first to operate from the terminal.

All the flights which used Terminal 1 were moved to the new Terminal 2, which opened in 2014.

In the future the plan is for Terminal 1 to be demolished and the new Terminal 2 will be extended in its place.

4. There is a "ghost" train station

The deserted underground ghost station is hidden beneath the bustling Terminal 5

Deep underneath the busy departure gates of Terminal 5 is a hidden “ghost” train station.

The station, which has no track in it at the moment, was included in the construction of Terminal 5, which opened in 2008, so new rail links to Heathrow can be created in the future, such as a western rail link to Reading and a southern rail link to Waterloo.

With the unused space spanning the length of 33 London buses, many don't even know of its existence.

5. Heathrow has been used for film and TV

Heathrow has featured on the big and small screen. Some of the latest filming to take place at Heathrow includes Hollywood film Red Sparrow starring Jennifer Lawrence and ITV Documentary Heathrow: Britain’s Busiest Airport.

For the 2018 fourth season of the documentary, the 14-strong crew drank 1,200 coffees during more than 500 hours of filming, across three months.

6. The control tower is very, very tall

The control tower is 87 metres high

The control tower at Heathrow was built in 2007 and is 87 metres high, which is nearly the height of 20 double decker buses stacked on top of each other.

Heathrow has planes from 81 airlines serving 204 destinations in 85 countries. New York is the most travelled to destination.

7. It's not just people flying in and out of the airport.

Normally we are more concerned with our own journey and suitcases to think about all the other things flying in and out of Heathrow – this is the hidden world of cargo. In 2017 Heathrow delivered 1.70 million metric tonnes of cargo.

More than 143 million kilograms of Christmas cargo flew via Heathrow to the world in the month leading up to December 25th 2017, a record to date.

As the biggest port in the UK by value, Heathrow plays a crucial role in delivering the essential ingredients for Christmas celebrations to British homes and homes all over the world.

Salmon was the most popular export to non-EU destinations overall by weight in November and December 2016, with 6,070,000 kilograms of fish (equivalent to approximately 480 New London Routemaster Buses) recorded as flying through.

8. 2017 was the busiest year ever recorded.

The year of 2017 was the busiest year ever recorded with 78 million passengers pass through the airpor

2017 was the busiest year ever recorded with 78 million passengers passing through the airport. That’s more than the UK population of the same year, which was more than 66 million.

This number of passengers in that year works out as an average of 213,668 a day and of this daily average, 51% were arrivals and 49% were departures.

Heathrow’s busiest day ever recorded was June 30, 2017, with 259,917 passengers. That’s getting on for three times the 90,000 capacity of Wembley Stadium.

9. Even runways need resurfacing

You probably know there are two runways and would expect them to be pretty big – the width of each is 50 metres – which is the length of an Olympic sized swimming pool.

The length of the northern runway is 3,902 metres (that’s 3.902 kilometres or 2.424 miles) so our maths tells us that is 78 Olympic swimming pools long, while the southern runway is slightly smaller at 3,658 metres – which is 73 Olympic swimming pools long.

Each runway is resurfaced every ten years.

In 2013 the southern runway was resurfaced, taking six months in a project costing £20 million.

A surface has to be suitable for planes to land on one hour after it is laid.

10. There are plenty of facts and figures to store in memory for the next pub quiz

There are mind-blowing figure facts about Heathrow which you can add to your general knowledge for the pub quiz

And finally, for those who like their quick-fire trivia, according to facts and figures for 2017, Heathrow covers an area of 1,227 hectors, and in 2017 it saw 474,033 flights, which was an average of 1,299 flights a day and employed 76,500 people.