'They thought the sea wall would save them' – Alex Thomson in the ruins of Kamaishi

We have seen destroyed factories, indeed whole towns, but we have never seen anything like the ruins of Kamaishi today.

It’s not just that the town has been largely destroyed – sad to say, that is a commonplace in the tsunami zone. it’s that so much had been done to protect this area from major tsunamis.

What I mean is this: the huge concrete sea walls built around the bay here.

You walk along them and they must be at least 25 feet high. At the top, you are walking along something perhaps eight or ten feet wide. And the walls fan out from your feet down to the water level 30 feet below, and at that point they must be at least 30 feet wide.

So you are talking vast amounts of concrete used here, because only this much concrete will protect the bay.

Well, that was the plan.

In fact, today, in the ceaseless, driving snow, you can see that the walls had been not just breached but ripped apart by the extraordinary violence of the tsunami.

That meant that the areas behind took the full force, which they never expected to take.

They thought they were safe. After all, that is why they built the walls in the first place, wasn’t it?

So it was, locals told us, that in one particular village, many people simple ignored the tsunami warning.

When they heard the sirens about 30 minutes after the tremors ceased, they took no action. When they saw the water was suddenly disappearing from the bay, they took no action.

When they saw this was no sudden low tide, but the water was really draining way out to see for more than a mile, some began to move, but still not all.

For when it came in, it would come in fast, but the wall would protect them. That is what they had been told.

Nonetheless, one thing that has survived today is the clear warning signs on the broken wall, telling people to go to higher ground if they heard the warning sirens.

So it was that we made our way to one of these villages. The last half-mile, an arduous and frankly perilous scramble through piles of rubble next to the deep waters of the harbour.

It was pretty obvious that few if any people had come this way since the tsunami. We checked – but no footprints in the snow or even the mud, where it was expected.

In the village itself no sign of the hastily aerosol-ed symbols which search and rescue teams spray on cars, vehicles and houses to show there are no bodies there.

Bodies there certainly are in this place – once you know that smell, you never forget.

But it would take a great deal of time to be able even to enter this place safely, let alone extricate the bodies of those who thought that the sea wall would protect them, because the sea wall always had.

Read more – Channel 4 News special report on Japan