"When you are in there, you don't sleep. There's no such thing as sleep. There were constant bombardments, artillery, and guns. You just become accustomed to it." He says that at some points there were rockets flying out from Gaza every few seconds.
His motives for fighting were not political. "The politics are out the window for me; it's a separate subject. I believe the main thing is just to protect the innocent civilians: the children, the women. That is my main objective. Everything else is secondary. So I know, when we don't sleep, that there are families who can sleep, who don't have to worry, who don't have fear. Just to know that my friends can sleep that extra one or two hours a night because I'm an extra soldier, or helping out with the gear, taking it kilometres on end. It gives me satisfaction to know that I can be there for them. For me, it is an honour; it's a privilege to be there to fight along with them."
Shimon says his family didn't sleep nights while he was there, and when he was able to use his phone he would receive a barrage of concerned and well-wishing messages from friends in England.
Although fighting was a bruising experience, he was touched by the support he received from the Jewish community in Israel and abroad. "We were constantly showered with gifts - crates and crates of food, and other gifts. Each parcel had a flag on it to show where it came from." He recalls how, while on 24-hour leave in Jerusalem, he was offered a free haircut, free drinks in a bar and had strangers approaching him offering money and cigarettes.
After such an intense period, the transition back to everyday life in England was tough. "One thing that every person who has ever been to war can relate to is going through the transition of going from that crazy war zone back to civil life. It is hard.
"I used to see my pupils dilated in the mirror, completely black. I felt manic. I couldn't even trust myself. The first two weeks were the hardest to get back to normal," he says.
"You've just got to accept it, you have to get to a point where you accept that what happened happened. Time is a great healer." Recent figures from the IDF say there are more than 100 young British Jews serving in the IDF. Though Shimon was born in Israel, the son of an English mother and Israeli father, he grew up in London attending Hasmonean boys school in Hendon. Living outside of Israel meant he could not be forced into Israeli conscription, which sees 18-year-olds carry out two or three years of military service. However, a tragic event when he was a teenager spurred him on to make the life-changing decision to enlist some years later.
In August 2004, his paternal grandmother, Shoshana, was killed in a bus bomb attack in her home town of Beersheba. It was one of two bus bombings that day that claimed the lives of 16 people and wounded 100 others. Shimon’s eyes turn glassy as he talks about it: "You don't believe something like that can happen to you. At that time, there were a lot of bus bombings in the news. But you never believe it can actually happen to someone you know, or a relative, someone close to you. The most traumatic thing was that I was very close to her and I spoke to her the day before. I suffered from depression from the event."
He says his family were dead set against the idea of him enlisting when he was 18, so he went to university to pursue his studies in graphic design instead. But he admits that, after the loss of his grandmother, the idea of enlisting constantly flickered in the back of his mind.
The emotional fallout of her death resulted in the breakdown of his parents' marriage, and Shimon says he has not spoken to his father in 12 years. He has four sisters, all of whom live outside of the UK.
When his mother, now remarried, made aliyah with her new husband it was the trigger for a 23-year-old Shimon, to take the step he had feared. Already employed as a graduate, he left his job to join to the IDF in 2010.
"After my grandma died I was lost, I didn't know what to do. I didn't know how to deal with it. But as I got older I realised this is my opportunity; I can face my fears. I didn't want to do it, but I had to face my fears and do what I believe in doing," he says.
While many teenage Britons who have dual Israeli nationality find themselves interrogated by Israeli airport security over their military service, Shimon found it was he who had to do the chasing to get the army to enlist him. He got in touch with aliyah organisation Nefesh B'Nefesh who in turn put him in touch with the IDF and together they "drove them mad" to get him enlisted.
"I had no idea what I was getting myself into," he says. "Before I was enlisted I had a fear: what is it going to be like? Can I cope? But I felt it was a duty for me, instead of supporting Israel in other ways, if I can serve in the IDF I would."
Defending Israel was a family tradition. His father was an IDF paratrooper and his maternal grandfather fought in the War of Independence in 1948.
Shimon served three years with the Golani unit training as a machine gunner. He served on the borders of Syria, Lebanon and Gaza and experienced a second tragedy when his friend and medic Netanel Moshiashvili was killed in action. He admits there were difficult times during his national service when he questioned whether he had made the right choice, but insists he has no regrets.
"As Jews, we have a responsibility to be there for our brothers. I feel that we all have this inner spark within ourselves to have that connection. That's one thing that I see as a blessing within the Jewish people: that in a time of need we are very, very close. We are like one nation, which is a special thing. And not just in Israel, but around the world."
Since returning to the UK last year, Shimon has set up his own company so that he can work freelance and ensure that he is able to return to Israel should he need to. Next month, he will go back for army training.
"I know that it's going to be tough, very intense. When you are there you think 'Why am I here?' But then you remind yourself of the reason. No one wants to be there, no one wants to go through the experiences and suffer and go through this whole crazy experience, but no one's got a choice, we just have to be there.
"Everyone does their small contribution and that becomes a combined force."
When asked if he has ever considered making aliyah, he says he has, but that the work and salary situation in Israel would be difficult. For the moment, he is happy to make his "contribution" in times of need, before adding: "I have always told myself: whenever the country needs me - and not in a heroic way - I will go back, no matter what."
*Name changed at the request of the interviewee
