21/03/2012 18:35 GMT | Updated 30/12/2012 18:39 GMT

My Week of Hell for Sport Relief

Being asked to do a challenge for Sport Relief is like being asked to be the god parent to an ugly baby. Despite knowing you will forever have a picture of an ugly baby hanging on your wall in case your godchild's parents come to your house, it is very difficult to say no.

How hard can it be anyway? You just smile by the font at the church at the christening, buy the child something silver and post a card once a year with an increasing amount of money in it. As for the picture, you just hang it in the room in your house you visit the least, although from experience hanging it in the shed always causes upset.

So when I was asked to engage in a 'Week Of Hell' that would involve transporting myself from Paris to London through the modes of transport that involved a bicycle, a rowing boat and some running shoes it was hard to say no. The call came as I was firmly entering middle age with a wider midriff than I had ever had in my life and my chosen mode of transport involved driving an automatic car so that when I did move anywhere I only used one leg. Sport Relief does sterling work within the UK and just when I was having increasing doubts about the wisdom of saying yes they took me to see some of their work in Sierra Leone. After that it was easy to stay motivated.

Day One - Cycling 185 miles from Paris to Calais

Although I have never rode such a large distance in a single day I thought this was going to be the 'fun' part of the trip. 18 hours later when I finished in Calais I had a slightly different view. My first major obstacle was navigating through the crazy Parisian traffic. And it wasn't long before I had a fall. I couldn't get my feet out of the pedal cleats quick enough at some traffic lights and, next thing I knew, I hit the deck in front of a bus stop full of Parisians who barely hid their disdain. To fall is one thing, but to do it in slow motion whilst dressed in unflattering lycra was obviously just too much for the style conscious French. But I dusted myself off, got back on the saddle and made it out of Paris in one piece. Just.

After nearly 100 miles I was joined by some mates who I had been training with and that gave me a lift as the darkness fell and the fatigue and pain took on another dimension. The most striking thing about the French countryside at night is that it is pitch black. Not dark, pitch black. There are no street lights for miles and the roads don't even have cat's eyes. And as the only illumination comes from a small light on your handle bars you only realise you are going uphill when you start to slow down and you feel the energy sapping from your legs. As you cannot see the apex this grind sometimes feels like it goes on for so long it was not hard to think we had been sent the wrong way out of Paris and had hit the Alps. I hit my bed around 5am with the scary thought that this was supposed to be the 'fun' part.

Day Two: Rowing from Calais to Dover

Just an hour later and it was time to get up to try and catch the high tide. Rowing for 26 miles was the bit that had made me most anxious. It's boring, exhausting and if you stop for any length of time, the tide takes you back to where you started. So feeling wretched already, rowing across the Channel was the last thing I wanted to do.

I was to be joined in the boat by Davina McCall, Freddie Flintoff and Denise Lewis. I already knew Freddie but had only met the others a couple of times, yet by the end of the day we had bonded after a truly unique experience. A lack of sleep had left my body so fatigued that I could barely speak, let alone row, and delirium had set in. I started seeing double and was so unintelligible during a radio interview Davina had to take the phone off me to complete the interview. I had well and truly hit the wall but the three of them carried me through whilst I filled myself with medication, food and rehydrated on supplies thrown on by the support boat. We finished strongly but had they not been in the boat I would probably now be drifting somewhere near Gibraltar.

Day Three: Marathon Run Number One. Dover to Faversham

After finally having a decent night's sleep, I woke up with renewed vigour and was on my way to running the first of three marathons back to back. It started off quite well, all things considered. I got a surprise visit from Radio 1's 'Comedy Dave' who joined me for the first couple of hours and then Dermot O'Leary took over the reins as we covered 14 miles before a lunch stop. It was pleasant morning having a chat but as any parent knows things don't always go to plan.

At lunch time I discovered my son had been involved in an accident where he had crashed his bicycle into a bus. His head had shattered the windscreen and all I knew was he had been taken to hospital, and as he was out of the country nobody could find any more information. In the absence of information I just had to run the next 10 mile section during which my Achilles on both legs began to tighten to the point of agony. At the final pit stop I was informed my son had been given the all clear and Dot the physio for the trip did just enough to allow me to carry on till the end.

The crowds of people who cheered me on lifted my spirits more than I could ever have imagined. People were beeping their car horns, others came out to jog along with me and some even stuffed money into my hand en route! School children came out of school and cheered which really was heart warming - why is it that other people's kids seem better behaved and less likely to crash into a bus and cause parents a heart attack? By the time I reached Faversham, after 26.4 miles of running almost flat out, I felt exhausted and exhilarated all at once. What a rollercoaster of a day.

Day Four: Marathon Run Number Two. Faversham to Gravesend

By day four, all the physical exertion finally caught up with me and I was sick in the night. I'd exercised to such extreme levels that my body simply rejected the food I'd put into it.

My wife Melanie joined me at the start and later I received a real surprise when Chris Moyles tapped me on the shoulder mid-run. The support he showed me throughout the challenge was amazing so it was great to have him there, running alongside me. Frank Skinner joined and kept me and the increasing hoards who joined us laughing - at times I felt like Forest Gump being followed by curious people wondering where the box of chocolates was.

The hardest part was starting after a pit stop. My legs would seize up despite the tape Dot was using on my legs to try and protect my Achilles. The fact that the tape was the same colour as a Smurf somehow was not as funny to me as it would have been had I not been in agony.

Day Five: Marathon Run Number Three. Gravesend to Trafalgar Square

I started the final day of my week of hell with two poached eggs on toast. It was more than I'd managed to eat in days but I was going to need the fuel. I had just over 28 miles to cover but it might as well have been 280. My body was in bits. I had shin splints that were causing me agony and my Smurf-like-Achilles were so sore Trafalgar Square may well have been Red Square, it felt so far away. But there was no way I was giving up now. So I just focused on putting one foot in front of the other, that was all I needed to do. Easier said than done.

Robbie Savage and my brother Eddie joined me for a stint. It was nice being joined by an ex-pro footballer and a bad dancer, you can decide who was which. I entered the city alone and felt suddenly alone. The big city almost swallowed me up, the cheering had stopped and rush hour proved hard to navigate. At that point it looked like I might have fractured my leg and the pain was so bad that every step was a struggle.

Then finally, after five excruciating and exhausting days, I reached Trafalgar Square as Liverpool FC's anthem You'll Never Walk Alone blared through giant speakers. There were crowds of people cheering me on and the reception was so uplifting, it brought a lump to my throat. But when Jason Manford announced my sponsorship total - a staggering £1,660,198 - the reality of the week hit me.

That figure says so much about the people of Britain. You'd never get any other country in the world to support my challenge in the way they have. And without a shadow of a doubt, it was the goodwill and generosity from the public that kept me going the entire way. Looking back now, I always knew that what I was doing would come to an end. But the money raised will change people's lives forever. So it might have been a week of hell for me, but for those who'll benefit from the donations, it'll mean a lifetime of difference.

John Bishop's Sport Relief Hell is on BBC One tonight at 9.00pm

John Bishop's Week of Hell for Sport Relief