IT IS the big moment.

Months of gruelling training, dieting and tireless charity fundraising will come to a head tomorrow when thousands of runners pound the pavements in the Morrisons Great South Run.

Crowds will line the streets when 25,000 people put their bodies to the test when the landmark race returns to Portsmouth for the 25th time.

And all of the participants have their own stories.

The famously ‘flat and fast’ 10 mile course route starts at Clarence Esplanade, Southsea, taking in some of the city’s most famous landmarks including the Spinnaker Tower, Southsea Common and Portsmouth Historic Dockyard before a grand finish back at on the Esplanade.

Double Olympic champion sailor Ian Percy OBE will officially start the race by sounding a starting klaxon at 10.15am.

He is running in memory of late sailing partner and friend Andrew ‘Bart’ Simpson who tragically died in San Francisco Bay in May 2013 in an America’s Cup training session.

Ian is fundraising for the Andrew Simpson Sailing Foundation set up in his memory.

Runners will be kept motivated by charity cheering points and boost zones run by local charities and organisations who are among those benefitting from runners raising tens of thousands of pounds for good causes.

Southampton teacher Mike Wood is tackling his 10th Great South Run and aiming to raise £600 for Catholic charity CAFOD.

The 51-year-old St Boniface Parish Church parishoner, who is a geography teacher at St Peter’s School, has already raised nearly £5,000 for the group and is collecting at justgiving.com/Michael-Wood17.

Reverend Bruce Deans will be running to support his wife Caroline – a lay preacher – who is undergoing treatment for breast cancer.

The vicar of St John’s Church, Fareham will run alongside congregation members and is urging people to donate to charities Cancer Research UK and Breast Cancer Care.

Jessica Denham, 21, from Fair Oak will be leading Team Sophie – a group running to raise money and awareness of brain tumours.

Inspired by her friend Sophie Peters, 27, who was diagnosed thanks to a visit to Specsavers.

Jessica, a marketing executive at Wessex Fertility, said: “We are doing the run to show her that she is not alone and she has our support. We don’t want anyone else to go through what Sophie has.”

The 21-year-old will be running on Sunday with her father Alec Denham, 56, and her sister Laura, 23.

Firefighter Andy Piller from Warsash is running in aid of Leukaemia Busters in memory of friend Richard ‘RJ’ Williams who died from the disease in March 2010.

The race is part of the Eastleigh fire station watch manager’s warm-up for the 2016 London Marathon and he can be sponsored at justgiving.com/Andy-Piller.

It will be a team effort when 31 staff from Aerial Direct in Gosport take on the challenge to help the telecommunications team smash through their £8,000 fundraising target for chosen charity Macmillan.

They are running in memory of many friends and loved-ones and can be sponsored at justgiving.com/AerialDirect2015.

Couple Emma and David Millard, both 28, are celebrating Hallowe'en early, dressing as zombies to fund the Southampton Hospital Charity.

Their niece Sophie Marie Arthur was saved by the unit after her premature birth in February last year and the Isle of Wight couple are collecting donations at justgiving.com/emma-millard4.

Ellie Dickens, 23, is taking to the course for Southampton General Hospital’s Teenage Cancer Trust Unit.

Her older sister Camilla, 25, was one of the first people to be treated when the flagship unit opened two years ago – but sadly died last year. Sponsor Ellie at justgiving.com/CammiRun.

Eastleigh MP Mims Davies is pounding the pavements for the Cardiac Risk in the Young (CRY) charity.

The big race is the culmination of three sister events taking place over the weekend launched with a 5km run today.

The shorter race features a women-only starting wave, staged in partnership with This Girl Can: Running, an advertising campaign urging women to embrace a healthier lifestyle.

The initiative’s poster-girl Sam Mollaghan, from Bournemouth, will be the wave’s honourary starter before running the course herself.

Hot on their heels is the Morrisons Junior and Mini Great South Run – the biggest children’s running event in the South.

This year it will be powered by magic with Disney-themed fancy dress 1.5km and 2.5km courses for children aged three-15 and a special character setting them on their way.

See greatrun.org/south for more information.