BELIEVE you can do it.

Five simple words that I hope will tip the scales in my favour on marathon day.

Physically, at the risk of tempting fate, I feel on track.

I recently completed my second 20-mile run, following the same route, and managed to trim ten minutes from my previous time (two hours and 47 minutes, compared to 2h 57m).

However, the thing that strikes me most, especially while deep in thought, pounding the streets, is the huge significance of mental strength.

It's been suggested to me that a marathon is as much about endurance up top, in your head, as it is down below, in your legs, and I'm beginning to see the wisdom of that notion.

Running a marathon is sapping, in every respect, and I know there will be times when ever fibre of my body is screaming to stop, walk or rest.

My challenge, therefore, is to ignore those thoughts, maintain a sense of humour and keep the little voice in my head subdued.

In preparing for London, I've swapped thoughts with many people, including Peter Gooding, a ten-time London Marathon runner and chairman of Harwich Runners.

It was he who promoted the 'believe you can do it' mantra.

"I could give loads of tips but if I had to narrow it down to one, that would be it," he told me.

"It makes all the difference because it's so important to stay positive throughout the race.

"Don't worry or think about the number of miles to go.

"Keep looking at your watch and keep your mind occupied, working out splits and remembering previous times.

"Rather than worrying about what you still have to do, flip those thoughts around.

"I used to get to 16 miles and think 'oh no, only ten miles to go. How depressing. After all those months of training, it'll be over in an hour'."

Wise words, Peter.

Hopefully, my cross country running, as discussed in the previous column, will help in that respect.

John Hyland, a vastly-experienced coach at Colchester Harriers, tells me that running these muddy, gruelling races will make me "mentally tough" for London.

He also offered important advice involving regular hill sessions to build up leg strength, speed work at my race pace once or twice a week and a long run once a week.

This, he believes, should help me run at an even pace.

It's going to be hard work, of course, and I'm going to need to summon a diehard determination.

However, I'm also expecting it to be great fun - an incredible, exhilarating and inspiring experience. Something I'll never forget.

While 26.2 miles represents a monstrous challenge, I'd like to finish by doffing my cap to Colchester and Tendring club-mate Jonathan Walton - currently in training to run a 100km ultra marathon from London to Brighton.

"I'm running this (ridiculous) event in order to raise money, and awareness, for an amazing charity, C.A.L.M. (Campaign Against Living Miserably)," he said.

"It was set up to tackle the terrible problem of suicide, particularly in men.

"I've had my own battles with poor mental health and want to give something back.

"It’s not an easy challenge, especially as I’ve had 20 knee operations over the years, but if I’m going to get people to sponsor me, and take note of the campaign, I have to do something a little crazy.

"My training runs are now getting up to the four and five-hour mark and the run itself is expected to take me nearer 14 to 16 hours.

"It'll probably involve me having to have fluid drained off my knee on many occasions.... yuck, I know!"

To sponsor Jonathan, visit www.justgiving.com/fundraising/runjonboywalton