Filming a news report on camera in an underground tunnel seemed like a good idea.

Until we were half way through our 450 metre crawl and the lights went out.

Stories about the tunnels between Egypt and Gaza usually involve a few shots of the entrance and the first 50 to 100 metres of the passage.

But we wanted to show the exact point where Palestinian tunnel smugglers have managed to cut through a thick metal underground wall that Egypt has pounded into the sand to try and break the smuggling trade.

This meant crawling all the way to the Egyptian border.

There are some tunnels large enough to smuggle a car into Gaza. We were not so lucky.

Our tunnel was no more than 1.5 metres high. If we were going to make it to the border we would have to crawl on all fours.

Two tunnel "guides", the cameraman and I started making our way through the tunnel with light provided by electricity cables hanging overhead.

The electricity did not last for long. Then we relied on dim lights from mobile phones to light up the way.

It was a dark and silent crawl though the tunnels of Gaza.

Last year some 1200 tunnels were operating. Today that number has dropped to around 400.

Egypt tried to block the tunnel trade at the end of last year by building a massive underground steel wall.

But it would take more than that to stop the smugglers. They use oxygen and gas torches to cut through the steel.

And so the trade of goods is flourishing. Fridges, generators, microwaves, food, fish and cigarettes come through the tunnels.

Israel claims Hamas also uses them for smuggling in weapons and money.

After 30 minutes, which felt like three hours, we arrived at the underground metal wall on the border with Egypt.

The smugglers had sliced through the steel. There was a gaping hole and the passage continued all the way into Egypt. But this was as far as we would crawl.

The smugglers say Egypt packed the metal wall with sand to make it vulnerable to collapse. We did not stay here for long.

After 30 metres of crawling back we stopped and our smugglers told us we would be catching a "train" to the entrance. We didn't take them seriously and wondered what they were really up to.

But true to word, three minutes later our train arrived.

It was a thick black plastic carriage, connected by a cable to the entrance of the tunnel. We hopped in, crouched down, our heads between our legs.

The camera was rolling, held by our "guide" who was at the front of the carriage.

I just hoped this train would not derail.

Seven minutes later a trip I'll never forget was over.

We were back at the entrance to the tunnel. Everyone was safe. We were whisked up the shaft to the surface, back into the blinding sun.

Outside Egypt is still building the metal wall, hammering thick pillars into the ground.

It seems a waste of time. As soon as the tunnel is blocked, smugglers say they will cut it open again.

With Gaza under blockade, the tunnel trade is thriving and not even an Egyptian wall can stop it.