Their mothers worked together and were pregnant at the same time.

They were born weeks apart and they attended the same nursery.

Now best friends Amy Thurston and Maisie Smith, both five, will support each other on their biggest journey.

Maisie was diagnosed with leukaemia in May and spent all of June and the beginning of this month in hospital after catching a potentially fatal infection.

She takes at least ten tablets a day and visits the Royal Marsden cancer specialist hospital at least once a week for chemotherapy.

She also spends a lot of time at Eastbourne District General Hospital.

But what keeps the bubbly youngster going is Amy who sends her best friend letters and pictures of the two girls playing.

Now Amy has organised a two and a half mile walk to raise money for Cancer Research UK.

Amy said: “The event is to raise money to help Maisie.

“Like me she is five. She is funny, smart and lovely, but most of all she is brave because Maisie has leukaemia.

“Mummy says this is very nasty and Maisie is fighting really hard, but the treatment is unpleasant and Maisie is spending a lot of time in hospital.”

Maisie’s mother, Sarah, 42, said: “We call her Amazing Maisie.

The treatment is never ending. She is five years old and this is her life. She is an amazing little girl. She processes what is happening very quickly and takes things very well. She is inspirational.

“She loves singing and dancing – she loves Katy Perry. And she loves swimming although she is not able to do that at the moment.

“Maisie is a very sociable little girl with lots of friends although Amy is her best friend.”

Maisie, who is currently at home with her mother and father Dominic, 40, in Eastbourne, hopes to be well enough to join Amy on the walk along the Cuckoo Trail between Heathfield and Horam from 10am on Sunday, July 24.

Mrs Smith said: “She is very excited.”

Amy’s mother, Nicky Thurston, 41, of Horam, said: “Maisie is a fighter and so brave.

“They are best friends. They met at nursery in Eastbourne and did not realise we knew each other because we both worked at East Sussex Fire and Rescue Service.”

Dogs are welcome on the walk.

To support the girls visit www.cancerresearchuk.org.