This will be one of England’s most challenging matches. And not just because they are facing the joint hosts Mexico in the iconic Azteca Stadium.

It has taken months of planning, a year’s worth of preparation and now, finally, England face Mexico in the last 16 tie of the World Cup.

England have known since the draw was made in Washington there was a string possibility they could face Mexico in Mexico City in the last 16.

The draw mapped it out that if England won their Group then that was the path facing Thomas Tuchel’s men in this World Cup. So, here are the challenges - and what England have done in preparation in line with FIFA protocol.

Hypobaric chambers

Last summer England players used hypobaric chambers, oxygen masks and heat chambers to prepare for this World Cup.

They introduced state-of-the-art technology at their training camp in Girona before their end-of-season fixtures with Andorra and Senegal.

It caused huge interest at the time and was clearly ahead of even where England knew where they would be based in this World Cup - or where they would play their games.

Cristiano Ronaldo uses the hypobaric chambers all the time. Some England players even have them at home.

No stone was left unturned.

Remote training

England stars were monitored by Whoop! devices given to them by FA medical and science staff.

They studied data, sleep patterns and energy as well as fitness on a regular basis while consulting with clubs.

When the draw was made in March, the research and contact was stepped up so that the FA staff knew exactly where every player was fitness-wise when they reported in March.

Training base

Now, look, England have caused a stir by training at Kansas City which is in the middle of the country and also having a pre-tournament base in Florida.

Florida was about sweating it out, a boot camp pure and simple and adapting to the conditions. Declan Rice insisted he could notice that he was sweating less after just over a week in the United States.

It was hot and humid and Florida and a real challenge - but one which the FA feel worked.

Once they got to Kansas City, it was about home comforts. Yes, it was humid and hot. But they looked at Dallas, New Jersey and other places and fancied Kansas.

Nice facilities, a good location and the players have enjoyed the anonymity and being away from any drama.

Flying

They have been able to fly home after every game and, unlike the Euros where they got back at 3 and 4am, they have got in at a reasonable time after every game.

That is clearly going to change after Mexico - but they will fly back to Kansas City whatever the result.

After DR Congo in Atlanta, the players got back to the hotel - and many went straight out on their bikes. At the next day at open training, even those who played hit the bikes.

Mexico

FIFA rules state that nations have to be in the host city at least 24 hours before kick-off to train, do media duties and be at the game.

From the quarter finals onwards, that will change to 48 hours as the competition hots up and the demands increase.

But the altitude is a challenge. Experts say the prime time to arrive in Mexico City is actually just six hours before - and then you do not feel the effects. That was not possible because of FIFA regs.

But anything between six and 24 hours is deemed OK. But 48 hours is the maximum time before experts believe ill effects kick in. Really it is 48 hours or a week to prepare. Nothing in between.

England are pushing the boundaries. Why? Many top athletes complain that the first night they see sleep broken and interrupted and that is something the FA are braced for. A bad night’s sleep on Friday but Saturday means they can sleep better before the day of the game.

It is as simple as that. What should they expect?

Even top athletes complain of shortness of breath, illness and light-headedness. There is no reason for it but it hits some harder than others.

The unique challenge of this tournament and why it feels unfair is that, back in 1986, England were able to train to play in Mexico when it was a one country World Cup. Now it is three.

Is that really fair? That is where sporting integrity kicks in. It feels definitely slanted and favoured towards Mexico who have played four games at the Azteca, won four and not conceded a goal. They are tenth in the world - and are a good team.

But the home record is disproportionate - just two competitive defeats this century - to the standing of the team. That is why Mexico have a huge advantage.

England players have been warned it may hit them in the first 20 minutes. But in Mexico, they believe the opponents tire in the last 20 minutes. Get ready.

Security and reception

England face a Welcome to Hell from the moment they arrive in Mexico City.

Ecuador were beaten in the last round and complained the night before the game their hotel was besieged by Mexican fans who played loud music, sounded horns and revved motorbikes. It kept the players awake and Ecuador made a complaint to FIFA.

This time, FIFA have spoken to the FA, they have promised a cordon around the hotel, and also a blue light escort from the airport and also to the stadium. Police and security are on red alert for the next 48 hours.

England players have also been given ear plugs, they have been given devices to listen to white noise and advice on best practice in every detail from diet, training and recovery.

The FA have taken every possible precaution. England are a better team man for man than Mexico. But with the fans in the Azteca and the growing sense of dirty tricks because of the farce over the potential kick-off change, we will only know after the game whether it all worked.

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