A British citizen living in Beirut said his family “feared he was dead” following Tuesday’s explosion.

Andy Kemp, 58, spoke of the emotional moment his son discovered he was still alive after the blast “turned his office upside down”.

He had been working less than half a mile from the explosion site when the blast saw glass shards fired into his head and neck.

He thought he had been blinded by the debris, before realising it was the blood from a head wound running into his eyes.

After the first explosion, Mr Kemp grabbed his phone and had enough time to type the words “uh-oh” in a group chat with his family before the second blast flung him across the room.

He said: “My office was turned inside out, and was on top of me. That was fairly scary. It went an eerie quiet after that, I just sat there, under a pile of stuff, the windows had been blown off, and everything had collapsed.”

Mr Kemp’s eldest son, Jack, 19, was at their apartment nearby when the explosion happened.

“Jack heard the first explosion, went onto his balcony, saw the second explosion and ran inside,” Mr Kemp said.

“As he was running inside, the two glass doors into the balcony followed him.

“He had an injury to his leg and assumed I was dead, freaked out and sprinted to the office. I met him coming the opposite way in the corridor, which was fairly emotional.”

His wife Jane, 51, daughter Phoebe, 12 and youngest son Max, 18, were unharmed after visiting the beach.

At least 100 people died and thousands more were injured in the explosion – and while there are no reports of British fatalities, details of UK citizens caught up in the devastation are still being established.

The father-of-three realised he was bleeding heavily and tried the hospital nearest his office, which had been badly hit.

He described the scene on the streets as “hell on earth”, with rubble everywhere, and people “compacted” into their cars on the streets.

He said: “They stuck me in the back of an ambulance with a dead guy and a bunch of people who weren’t doing very well.

“There was so much blood on my phone, I couldn’t use it. I could see my wife was trying to call me, but when I tried to swipe to answer, my phone was slicked with blood.”

He said he was “one of the lucky ones” as shards of debris narrowly missed piercing vital veins in his neck.

Speaking during a visit to Warrington, Prime Minister Boris Johnson said he was “appalled and shocked by the scenes in Lebanon”.

He said: “Our sympathy is very much with the people of Lebanon, of Beirut, and all the victims, their families, all those who’ve lost their homes — hundreds of thousands of people who have seen their homes damaged, one of the worst explosions we’ve seen in modern times.

“The UK has sent HMS Enterprise to help survey the port to see what we can do to help with the repair of damage.”

He said the Government would be sending a medical team and support package of £5 million to aid recovery efforts.