What he did learn was that six months of healthy eating and constant physical training are paying off. His body, it seems, is actually in great shape. His heart is strong. His lungs are good. His blood pressure is fine. There is nothing actually wrong with him other than he took a massive beating from a very big man which caused a great deal of shock to his system. Then being bedridden for several days meant he weakened. His energy levels lowered. His internal resources focused on healing and mending the damaged bits, which in turn left him tiring easily.

Despite all of that, and despite the utter desolation of knowing Safa and Harry are dead, his mind is once more his own, and to compensate for the sense of bereavement he reminds himself constantly that he has a time machine and will go and get them back.

That thought drives him, generating a relentless, unstoppable energy. He trains. He eats. He sleeps. The swimming tank is fantastic. Ben only ever swam for leisure and the tank, as small as it is, means he can build up his technique for powering through an ever-increasing current. It also means he gets used to the mask, the flippers and exerting himself while having the mouthpiece of a breathing tube between his teeth.

He also runs. Not far at first, but as the days go on, so he covers more distance. Up and down the side of the bunker, where Safa and Harry drilled him relentlessly. He remembers the lessons. He remembers the warm-ups, the stretches, the warm-downs. He remembers the circuits and the types of food that Safa told him to eat. Proteins, carbs, fats and nutrition.

Ben knows, despite the urge gripping him to go now and dive through the portal to save them, that he has one shot and one shot only. Malcolm and Konrad will never come after him. Roland has made that clear. Roland will not risk losing them in addition to Harry, Safa and Ben if he doesn’t make it back. So that means Ben has to get it right the first time.

The evenings are the worst. In the day, he can focus on the training. He can swim, take a break, swim more, do some other exercise then go back to swimming. He can fire pistols at targets and use the metal detector to hunt for the casings on the grass. He can find focus and things to occupy his mind, but when night comes, so the emptiness of the bunker becomes striking.

Instead, he takes a bottle of beer and sits outside to watch the sunset that Harry and Safa watched so many times. He sits next to two empty chairs then returns to their rooms that have changed so much but that still hold the smell of them. The bittersweet scents that invoke too many emotions.