By James Kelly & PA MediaBBC News
PA MediaBarney will take on the walk alongside his father Darren (left) and godfather Bradley (right)A boy who is taking on a "midnight march" to raise funds for the hospital where he had "life-saving" surgery as a baby has said he thinks "the hardest part will be staying awake".
Barney, from Bristol, will join his dad and godfather for a 12-hour trek around London on 22 December.
The nine-year-old hopes his exploits will fund play equipment for Bristol Royal Hospital for Children.
His father Darren said he was "proud" he had "a little boy that cares".
Barney's fundraising efforts will see him set off from London's Paddington station on 22 December and walk past Wembley stadium, the Houses of Parliament, The Shard, Tower Bridge and Brick Lane, before returning to the station to catch the first train home on 23 December.
'Really happy'
Barney said he would prepare for the overnight walk by staying up all night on 21 December and then sleeping through the following day.
"I'm nervous and excited, and I reckon the hardest part will be staying awake," he said.
Asked what will motivate him on the walk, he said he would "put some Oasis on".
His dad said Barney, who had surgery to correct two holes in his heart at the age of 11 months, "loves Liam Gallagher", but was equally committed to his charity work, which has already seen him raise a substantial amount for the hospital.
"He takes great pride in his fundraising and we always look forward to the day together," he said.
"I'm really proud that I've got a little boy that cares."
PA MediaBarney was treated at the Bristol Royal Hospital for Children as a babyHe said he would always be thankful his son had the "life-saving" procedure.
Recalling the day of the operation, he said Barney "woke up straight away" afterwards.
"It was as if somebody flicked a switch, his face was red and he ate a whole Twister ice lolly," he said.
"He was really happy.
"We were really grateful to the children's hospital and the charities that work in conjunction with them."
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