I’m writing this from Sendai in Japan, in the aftermath of one of the biggest earthquakes in the country’s history.

Amid rising fears about the quake’s impact on Japan’s nuclear power plants, the death toll from Friday’s quake is now feared to run beyond 10,000. Alex Thomson has become one of the first foreign journalists to get right into Minamisanriku – a fishing port of 17,000 people where up to 10,000 are missing.

He encountered terrible scenes of loss of life, devastation of homes, and grief on an unimaginable scale. I saw his team return to our hotel here in Sendai – shocked to the core by what they had seen.

I and my team have been out around this significant port city (pop one million), much of it surprisingly undamaged. The rest of it, almost beyond recognition.

The tsunami swept across farmland eight miles from the sea, sweeping splintered wooden houses, shower cabinets, washing up basins, clothes, and of course cars in which many people died. The city’s ring road provided a raised trap against which all this detritus piled.

RTR2JTXX Japan: loss of life, devastation of homes, unimaginable grief

The wave from a tsunami crashes over a street in Miyako City, Iwate Prefecture in northeastern Japan

We have watched the highly efficient search for the dead. Beyond the remarkable survival of the man found floating on his roof, 10 miles out to sea, few people have been pulled alive from all this.

But it is the nuclear threat that is paramount. The authorities are engaged in a desperate battle to prevent another explosion, after the roof of a building blew off at a Fukushima nuclear plant on Saturday.

A second reactor at Fukushima appears to be in meltdown, a second plant in the same region is also in trouble, and yet another nuclear station is facing exactly the same problem with cooling system failure. The authorities are pumping sea water in to cool the reactors, and fortunately the wind is in a good direction, but the Japanese Government is already being accused of downplaying the scale of what is happening.

But this also needs to be balanced against the amazing dedication of Japanese rescue services, who are rapidly moving in on the worst of the devastation.

Channel 4 News is specially extended and starting at 6 tonight, Julian Rush has a highly informed take on the nuclear crisis, Alex and I will be live in Sendai. Krishnan is handling the debate on the nuclear issues – including the question of whether this will affect the world’s attitude to nuclear power in the future – and the rest of the day’s news.