Steve Irwin's daughter Bindi has paid tribute to her father on what would have been his 55th birthday

Alongside the photo, she wrote: "Always in our hearts. (sic)"

Steve was famous for his show, 'The Crocodile Hunter', and whilst filming for an ocean documentary in 2006, the 44-year-old conservationist was stung in the chest by a stingray barb, which killed him.

Bindi previously paid tribute to her dad when she turned 18 last July.

At the time, she wrote on Instagram alongside a baby picture of herself with her parents: "Hello lovelies. Well today marks 18 years of life for me, here in Australia and I really don't know where to begin in thanking so many people for an unforgettable journey so far. So I think that I'll start here, with this photograph.

"This photo was taken within the first year of my life. To be perfectly honest life has changed in a million ways since this photograph was taken. Along the way we gained another incredible part of our family, my brother Robert.

"Our conservation work with Wildlife Warriors took off around the world. Our home, Australia Zoo continued to expand and has become the greatest zoological facility on planet earth.(sic)"

Bindi, although only eight at the time, spoke at her father's funeral, and 10 years later she wrote of what a "superhero" he was to their family.

She continued: "Our Dad, Mum's soulmate and a superhero for us all, passed away. However, since this photo was taken, 18 years ago, one life ingredient has remained, unchanged, unbreakable. That is the unconditional love that is shared between my beautiful little family and the loyalty we have to each other and everyone else who has taken this journey with us.

"I don't think that when this photo was taken even my beautiful parents could have known what life would evolve. I know that I am endlessly grateful for the love and light I have been given since Day 1 of my life. (sic)"