The mum-of-two from Paulsgrove has lost an incredible seven-and-a-half stone in weight and last month achieved her ambition of running in the world-famous event.
But it has been a difficult journey for the 26-year-old.
Her weight loss only began after she discovered she was pregnant and then gave birth just days later.
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Her weight masked her pregnancy so much that she didn’t have a clue she was expecting until she was approaching her 40th week.
That was the catalyst she needed to inspire her to shed the pounds.
‘I always needed to do something about my weight,’ she says.
‘I was large all my life. But in March 2009 my dad was diagnosed with terminal lung cancer.
‘Then in the July of that year I found out that I was nine months’ pregnant.
‘I hadn’t noticed. With the stress of my dad’s illness and the fact that I was so large, I didn’t know.’
Remarkably, Nikki found out she was pregnant on July 7, 2010. She saw a midwife three days later, who confirmed her pregnancy and said she was one day overdue.
Her son, Tyler, was born just10 days later on July 20.
‘It’s all such a blur now,’ she recalls.
‘My mum was suspicious. My feet were swelling, but I just thought that was because it was hot. My mum got me to do a pregnancy test.
‘I was 18 at the time. I had been out drinking and clubbing while pregnant, but I didn’t know.
‘My family just pulled together really quickly to do what they could. It gave my dad something to hold on to.’
But sadly for Nikki and her family, her dad, Kenny, died three months later, aged just 55.
‘I lost my dad in the October,’ she adds.
‘He held on for seven months after the diagnosis. I think it was having a baby around that kept him going. He just fought it every day by himself.
She adds: ‘My dad was always really worried about me because of my size. So I walked through the Slimming World doors in January 2010.’
At the time, Nikki weighed 19 stone.
‘I knew that something had to be changed,’ she says.
‘I didn’t want my son growing up being bullied because he had a big mum. I was bullied all my life and I didn’t want that to happen to him.
‘The first year I only lost a stone because it was a difficult time without my dad. But one morning I woke up and it was like someone had flicked a switch in my head.
‘I knew I had to do something about it.’
And she did – Nikki lost five-and-a-half stone in a year.
As well as eating healthily, she started to exercise .
‘I began using the Wii at first. Then my older sister convinced me to go to Zumba classes with her. We did that for quite a while.
‘Then a friend of mine wanted to go running, so I decided to go with her. I couldn’t run to start.
‘People would shout things at me, which hurt.
‘Then I started kickboxing classes and I have a black belt now. ‘
In 2012, Nikki fell pregnant again and gave birth to her son, Tommie, now four, the following April.
But she didn’t let pregnancy set her back and prevent her from reaching her goal and in 2014 Nikki completed the Great South Run for the first time.
By November, 2016, she had dropped an incredible seven-and-a-half stone and weighed 11 and-a-half stone. She went from a size 24 dress size to a size 12-14.
She smiles: ‘My mum still beams with pride. It’s an indescribable feeling.’
She was entered into the London Marathon as part of a team from Slimming World.
When the big day arrived,Nikki wasn’t nervous.
‘I was really calm,’ she says.
‘The atmosphere was incredible. You can train for it, but I probably would never have crossed the finish line if it wasn’t for the support I received along the way.
‘People are shouting your name and offering you sweets. I cried for the last mile .’
Nikki completed the London Marathon in six hours and six minutes, raising money for Cancer Research UK.
She says: ‘Even now I’m still a bit in shock that I have done it.
‘Even if I never do anything like that again, no-one can take that away from me.’
MAKING A CHANGE
When Nikki decided to make changes to her life, she soon discovered a love of cooking.
She swapped her unhealthy diet for preparing healthy, wholesome meals from scratch. These have included her favourite dish ‘nacho-style chilli feast’, with plenty of fresh vegetables.
She says: ‘I was so nervous before joining Slimming World, but I soon realised I needn’t have been.
‘I got a fantastic warm welcome from the group and when the consultant explained the eating plan, I couldn’t quite believe it.
‘Losing weight without going hungry, while still enjoying all my favourite meals, just by making changes to the way I prepared and cooked them, has been amazing.
‘I’ve never eaten so well in my life.’
Visit slimmingworld.co.uk to find out more.