Tony Bellew conquered the cruiserweight division to become WBC world champion in a stellar career but in his latest BBC Sport column the retired boxer brings us up to date with an altogether different kind of battle.

Painful. I have taken my smacks in a boxing ring but that is the only word I can use to describe my recent foray into SAS training.

As you may have read in the papers or have seen on social media, on Monday on Channel 4 you can see me join 11 other celebrities (I never class myself as a celebrity) on the hit TV show 'SAS Who Dares Wins Celebrity'.

For those who have not seen the show before, a team of former soldiers led by former Royal Marine Ant Middleton take a group through gruelling SAS selection training for over a week - though few make it that far.

Former footballer John Fashanu and The Only Way is Essex star Joey Essex are two of the celebrities in there with me at a base set in what felt like a punishing wilderness. It was actually the island of Raasay, just off the coast of Scotland.

You'll have to watch the programme to see how far I got in the process. What I can say is the whole thing is a torture and you find yourself looking in the mirror day after day, asking questions of yourself that you never thought you would.

The tasks you're asked to undertake include running face-first down a cliff face when your body and mind tell you not to and being submerged in the ice cold sea until one of you quits - and if the water doesn't break you, the heights and deadly drops you have to conquer might do.

Throw in what the military men label 'sickeners' - where you think you've conquered a challenge only to be told you have more to endure - and it's brutal. Honestly, what you see on television looks hard but when you are there, the challenges form part of a package that slowly debilitates you.

Your dormitory gets stormed in the middle of the night and you can't get a wink of sleep. When I got home I felt the after-effects as I spent around three weeks waking up sweating in the middle of the night and could feel myself looking for exit points in rooms at all times.

Bellew took orders from show host and former Royal Marine Ant Middleton (right)

It was so intense and at one point emotions poured out of me when I was faced with a particular task which quite simply pushed me to my very limits. Some painful memories came flooding back.

My motivation for going in there was that after I retired from boxing, and with my ambitions ticked off by the age of 36, life immediately after retirement felt pretty hard.

I have always admired the men and women in the military so when I got the call I thought it sounded perfect. Then the apprehension set in. I just didn't want to go on and embarrass myself like some old has-been.

The night before, I was going to pull out. I'd be living off rations, deprived of sleep and I just thought I'm bound to go in there and be instantly perceived as a tough-guy boxer who should thrive in this environment when actually I'm not that type of person in day-to-day life.

Another boxer pulled out close to last year's show but as I'd given my word, in I went. I half expected there to be some kind of plush secret rooms for celebrities away from the cameras but I ended up sleeping for over a week in the same clothes. To put it mildly, I absolutely stank.

I'm a fussy eater so food was a problem. The best thing I had to eat in there was a rabbit, which we were shown how to skin and cook. As I put this column together I am about to eat fish and chips. It is safe to say I appreciate such treats a little bit more now.

But the military men tell you everything you go through in SAS selection is for a reason. The limited food, the lack of sleep - it's all for a purpose. When you're woken at 2am to stand outside for a horrible physical 'beasting', it is not because they want to see how long you can hold a weight up for, it is to shatter you, wipe you out and break you either there and then or during the next day's task.

I was just looking in the mirror and and thinking I just can't let them beat me, even if my toe nail is hanging off.

Bellew (right) is joined by the likes of television presenter Anthea Turner and dancer Brendan Cole on the show

I have always had certain trust issues, so when you're lumped into an environment like that with strangers and you have to rely on one another, it is tough.

I built rafts, constructed huts and faced the elements head on but on a deeper level I took so much from it.

I learned how unimportant a mobile phone is and when I got back home I ended up turning mine off for days.

Above all else, it brought home the importance of family. That is something none of us need reminding about given the current times we are living in. Ultimately, the most important thing we all have is within the four walls of our homes.

Trying to do right by your family is no easy task but being in situations where you miss them badly makes you want to be the best version of you when you're with them.

Hopefully you and your family can watch and share a few laughs while seeing me suffer over the coming weeks. It was without doubt one of the toughest - and best - experiences of my life.