Kieran Perkins, 35, a father of four, kept his plans from his children’s mothers and his family, he told the BBC.

He said: “I didn’t even tell my mum. I just thought because I’m only away for a short period of time … I didn’t want to worry anyone.”

Perkins, who spent five years in the Army, said that he was not planning on a long war.

He only wanted to stay in Ukraine for two or three weeks before returning home.

He told the BBC that he had childcare responsibilities and a birthday coming up, adding: “I’m not expecting to get to the front line in that time.

“But if everyone chips in to help, then it takes the weight off the people that are really working hard right at the front line.”

Perkins was an armoured vehicle driver with the Princess of Wales’ Royal Regiment and served in Afghanistan.

He met up with two fellow former soldiers at Stansted airport after exchanging messages with them online.

The three of them met for the first time at Stansted before they caught a £20 flight to the Polish city of Krakow.

On their first night in Poland, the men slept out outside Przemyśl railway station, before walking across the border into Ukraine the following morning.

They spoke to a reporter from the BBC in Ukraine, a few miles from the border with Poland.

The trio, who served in the Army for 19 years between them, were waiting for transport to Lviv, along with other recruits.

Perkins said: “We were stopped by police on the way out. They said, ‘fair play to you.’ As far as I’m aware we’re not doing anything wrong.”

One of the other two men, CJ Darton, who served with the Royal Anglian Regiment, said: “I just can’t sit at home and watch what’s going on and carry on as usual.”

Asked whether it was the excitement of war that had brought them to Ukraine, Darton said: “Anyone who thinks we’re war junkies or war tourists needs to stick to watching the news.

“There is no excitement to war. There’s nothing nice about dead kids at the side of the road.”