On board the new Eurostar, the sleekest under-sea train (pictures)

Meet the Eurostar e320, one of 17 brand new trains Eurostar will be putting into service later next year as part of a £1 billion ($1.57 billion) upgrade to its trains, networks and stations.

Eurostar is the service that allows you to catch a train from London to Paris and beyond. There's a sea in the way, of course, but Eurostar dives under it, using the 31-mile Channel Tunnel.

Work on the tunnel began in 1988, and it was finally opened for business in 1994, costing £4.6 billion. It was a hugely ambitious project, but its completion allowed for a quick and comfortable way of travelling between England and mainland Europe without having to fly or use the ferry.

Eurostar is celebrating its 20th anniversary this year, and what better way to celebrate than with a fleet of shiny new trains?

At an unveiling in London's St Pancras station, we hopped on board the new train to see what it's like.

The interior design is bright and welcoming. LCD screens drop down from the roof to give journey times and destination information.

Eurostar said it crammed in 20 percent more seats but also improved leg room. It managed that by using much slimmer seats.

The new trains can fit 894 passengers at full capacity and free Wi-Fi will be available throughout the train -- it's the first time wireless internet has been available on a Eurostar train.

When you log on, you'll be immediately met with Eurostar's portal, which will bring you live journey details as well as travel advice for your destination, including things to see and do and weather forecasts.

Eurostar "has become a real bridge between the countries, the cities and the people," Eurostar Chief Executive Nicolas Petrovic explained at the train's launch event, which also marked the company's 20th anniversary.

Part of the upgrade includes extending Eurostar's reach to Amsterdam and Marseille -- journeys that will begin next year.

Here's the e320's cockpit. It's the best view you can have when hurtling across the European landscape.

I have no idea what any of the buttons do, although I'm assuming that big red one stops the train pretty quickly.

At least the driver gets this lovely, big comfortable chair.

Here's the business class section. Business class will of course cost you a lot more than a standard ticket, but it has a whole bunch of perks.

Business passengers get handy smartphone stands built into the back of the chair in front. No more arm ache when you're holding your phone up for hours on end.

UK and EU power sockets are attached to every seat on the train, but business seats also have USB outlets to charge phones and tablets.

World-renowned chef Raymond Blanc is in charge of the business-class catering for Eurostar.

"There'll be six changes every month to the menu," Blanc explained to me. "Everything is seasonal. Eurostar understands seasonal well. With local, seasonal food, you don't have to import your food. That means no pollution, you help your local farmers and you help your local village keep its post office.

"If the train is leaving England, you celebrate English food," he continued. "When you travel from France, you celebrate French food.

"I know the sourcing of all our food. Eurostar is the only [travel] company that has two stars from the sustainable restaurant association," he said. "We're as local as we possibly can be."

The trains are all electric and were rigorously tested for aerodynamics in wind tunnels to make them more efficient than the previous models.

Siemens, which makes the trains, explains that external components like the air conditioning units have been integrated into the body of the train to reduce wind resistance.

Those of you not forking out for business class will need to wander down to the buffet car, which is designed in the same light, airy manner as the rest of the train.

It takes around four and a half months to build each of the 17 trains -- and that's before the months of testing.

Although this model is finished, it will be undergoing more testing before being put into service next year.

Here's the old Eurostar train. Not quite as fancy is it? As part of Eurostar's £1 billion investment, the existing fleet will be upgraded with a host of new features.

The physical dimensions differ between the old and new trains, however, so they won't look identical.

Tables on the train have been made very slim to give more room to easily slide into the seats. Extra table space comes from a slide-out part, if you need to fit your laptop.

I put my considerable experience at sitting in comfortable places to use by testing the chairs. My conclusion? Enjoyably supportive.

St Pancras station is one of only two stations in England where you can catch the Eurostar -- the other is Ashford International in Kent, shortly before the tunnel.

Editor's note, 14 November: A previous version of this slide stated that St Pancras was the only Eurostar station in England. That is not the case.

First opened in 1868, St Pancras is an impressive building on the inside. It's Grade I listed, meaning it is "of exceptional interest".