In 2003, I failed two of my four professional accountancy exams. ICAS' policy at the time was that students were unable to carry forward any passes, so I had to re-sit all four exams again. I knew that if I failed again I would lose my job, since that was Deloitte’s policy.

I sank into a spiral of anxiety, insomnia and depression. I had dropped out of University twice, and taken five years to complete my undergraduate degree. It had seemed impossible for me to secure a role with a Big 4 firm, but I had managed it. I felt certain that failing my exams again and being made redundant would be the end of my career, and effectively my life.

I was consumed by helplessness as my anxious thoughts generated feelings of despair. I became withdrawn, and found solace in alcohol and other drugs. I was unable to sit my exams.

Eventually, I reached out for help. I was off work for a month and was treated with antidepressants and prescription sleeping pills. This created enough safe space for me to overcome the anxiety about the future, and I returned to work and was able to re-sit my exams.

In the summer, I travelled to South Africa with Glasgow Hawks RFC as we completed an unbeaten three-match rugby tour, which sparked an incredible run of three consecutive national championship victories.

On tour in South Africa, I took a call from a partner at Deloitte. I had passed three exams, and failed my tax exam for the second time. On my return home, I was made redundant.

I was devastated, and needed to channel all of my emotional energy into something positive. In September 2003, I signed up for the Marathon des Sables, a 150-mile ultramarathon in the Sahara desert – known as the ‘toughest footrace on earth’. I would be running the equivalent of six-and-a-half marathons in 40 degree C over 7 days while carrying all my kit.

Over the next six months, I secured sponsors, sourced specialist kit, sought media coverage, trained and raised over £5,000 for a charity called Facing Africa. In December 2003, I found a new job with a small firm in Edinburgh, which meant I could transfer my CA training contract and complete my training.

I continued to train twice a week and play on a Saturday for Glasgow Hawks, so my longest training run was only 13 miles on a Sunday afternoon.

During the event, I suffered infected blisters and became severely dehydrated - I was given three bags of fluid intravenously at a check-point.

The physical hardships were extraordinary, but the mental challenge of pushing my broken body day after day up and over huge sand dunes and across dry, rocky lake beds in 40 degree heat became so much more.

Physical fitness became almost meaningless – the challenge was almost entirely in my head. At many points, I wanted to give up, and many others did. One poor soul lost the entire sole of his foot to a giant blister, but continued.

Hugh Barrow, then club secretary of Glasgow Hawks and a truly world-class runner in his day, had sent me an excerpt from the poem ‘If’:

"If you can force your heart and nerve and sinew, To serve your turn long after they are gone,  And so hold on when there is nothing in you, Except the Will which says to them: ‘Hold on!’

I began to repeat this like a mantra over and over. With ten miles still to run of the fifty-mile long stage, I began to bawl. I knew the end was in sight, and I knew I could finish the event. I was totally overcome with emotion.

On the fifth day, I ran the marathon stage with a guy who suffered from agoraphobia – he had come here to the wide open vistas of the Sahara desert to overcome his fear in order that his infant daughter’s quality of life would not be impaired. He simply wanted to be able to play in the local park with her. I was again moved to tears, and felt inspired beyond my normal boundaries of understanding.

I knew now there would be no giving up. I had too many people supporting me. I had sacrificed so much to be here. I needed to overcome my own fears and self-doubts.

On the last day, I ran the final half-marathon stage in a little over two hours. My pack was lighter, as most of my food was gone. I was filthy and bedraggled, but when I crossed the line I had a rare feeling of elation that I have never experienced since.

I watched another runner cross the line holding a short piece of rope in front of him. Holding the other end was another runner. Suddenly, I realised that the runner behind was blind, and the runner in front was his sight guide. I was amazed, and overawed. I had achieved something I could only have dreamed of, but this brave competitor had done it without the use of his eyes.

I felt transformed. I would no longer let my fears hold me back.

Failing my professional exams became the most transformative experience in my life.