The second of four brothers diagnosed with one of the world's rarest genetic disorders is undergoing tests ahead of his transplant operation.
Daniel is to undergo the tests in Great Ormond Street Hospital
Joshua, 12, Nathan, 10, Daniel, eight, and Luke Hartley, four, from Romsey in Hampshire, have a genetic disorder which attacks the immune system.
The only cure is a bone marrow transplant and after a nationwide appeal matches were found for the boys.
Joshua has had successful transplant operation and now it is Daniel's turn.
Thousands of people contacted the Anthony Nolan Trust to volunteer as donors for the boys - who have X-linked lymphoproliferative disease (XLP) - after appeals on the BBC and other media.
Allison Hartley was matched as a donor for her son Joshua, who is recovering at home after a successful transplant operation on 9 June.
Daniel is now due to attend Great Ormond Street Hospital in London for a day of tests to make sure he is fit enough for a transplant operation at the end of
Joshua is looking forward to going back to school
His father, David Hartley said: "He is going to spend the day in hospital for between seven and nine standard tests which range from having his teeth tested to a chest X-ray and checking his lung function. We'll be bringing him home the same day.
"We know from Joshua that they lose about 10% of body weight as a result of the transplant so it just allows them to check everything is all right and we are not anticipating any problems because Daniel is fit as a fiddle."
Daniel was being taken to the Rainforest Cafe in London's West End as a treat afterwards, and Mr Hartley said: "It's all he's thinking about. He's just
excited about the animated gorillas and elephants."
Mr Hartley said: "Josh is doing very well, is putting on weight nicely now.
"He can't wait to get back to school. He gets bored with just mum and dad at home."