Twelve-year-old Luke is passionate about black history and wants people to realise how important it is.

Ten-year-old Caitlin wants to become a conservationist when she's older. She is passionate about teaching other people how important our world is, and needs a den where she can research.

11-year-old Maariya was scared of going underwater but overcame her fear a few years ago. Now she loves swimming, snorkelling and all things underwater.

Eight-year-old Nathan loves learning all about the rainforest from his dad and wants a den so he can feel like he is deep in the Amazonian rainforest every day.

Becca and her twin brother, Charlie, loved their new chinchillas. However, one of them was pregnant and gave birth and the only way to save them from being rehomed is to have a chinchilla den.

Twelve-year-old Ashley needs an opera-themed den so he can sing to his heart's content. He has Tourette syndrome and singing helps him to overcome it.

Eight-year-old Mei is half Japanese and loves learning more about Japan's culture. She doesn't get to visit as often as she would like so needs a den where she can celebrate her Japanese heritage.

Nine-year-old Jothi had an illness as a baby that caused his legs to not grow properly, meaning he can't visit his favourite crazy golf course. Jothi needs a crazy golf den he can access all the time.

11-year-old Holly has chronic actinic dermatitis, eczema caused by UV light, and needs a calm and relaxing den to help forget about it.

Ten-year-old Evie wants a den where she can spend quality time with her aunt, whose chronic rheumatoid arthritis means she is unable to get up the stairs to Evie’s room.

Eight-year-old Matthew needs a den so he can teach his sister the board games he has grown to love.

Ten-year-old twins Becca and Lottie need a den so they can enjoy wildlife and bugs together. Becca has cerebral palsy and her wheelchair makes it difficult to play in the garden with her sister.

Joe and Meryl look back at all the amazing dens built throughout the series and reminisce about the great kids, the tense surprises and the big reveals.

Joe revisits the Queen Victoria, Australia, Sewing and Army Coding Dens.