Natalie Collins, 59, broke down as she said: “This is just opening old wounds for us, the door never closes, the police are wasting good taxpayers’ money and their time, they’re never going to find William — I just know in my heart he’s dead.

“I know exactly what’s happened, someone’s taken him and done something to him. Brendan (William’s father) says it, too, he believes William’s gone.”

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William’s abduction on September 12, 2014, sparked one of the biggest manhunts in Australian history and has gripped the country since.

The three-year-old disappeared dressed in a Spider-Man suit from his foster grandmother’s Kendall home but no trace has been found of him and this week police began a new hunt for the youngster.

Ms Collins, a cleaner, said she and her family were not informed of the search for fresh evidence involving a 50-strong force that has already unearthed a toy hidden in the undergrowth on the NSW mid north-coast, where the mystery began almost four years ago.

It is too early to link the toy and bags of evidence collected to the boy, who was three when he vanished. It will take four weeks to scour the 3 sqkm of bushland.

Police said the difference between this search and the initial hunt when William disappeared was “a focus on deliberate human intervention”.

“What clues are they looking for? William can’t even walk that far to Kendall, he’s not there,” Ms Collins said through tears.

“Brendan (her son) knows in his heart of hearts his son is dead.

“His mum Karlie has his other children, it’s hard for him dealing with that.

“He hopes they find something but he is not hopeful, maybe finally we’ll be able to get on with our lives, maybe the search will help us do that.”

Mrs Collins’ call came after William’s biological father laid bare his despair since his son’s disappearance, revealing he had searched in vain for him, digging in bushland with a shovel since his release from Silverwater jail in April over drugs and theft charges.

Speaking to his son through The Daily Telegraph, Mr Collins said: “I’m so sorry for whoever’s done this to you, William, I don’t know who took you in your Spider-Man suit.

“I’ve been out looking for you with a shovel digging in bushland … I know there’s no point.

“I think you’re dead, I think someone has hurt you bad. I’m so sorry I couldn’t help you.”

Mr Collins also revealed he ran way with his son for seven weeks when William was nine months old until authorities took him into care.

“I know I’ve had a history of drugs problems but I’d never harm my boy,” he said. “DOCS took him from me to keep him safe and now … he’s probably dead.”

Mr Collins, who struggles with depression and is living with his mother, said police questioned him over the nation’s most baffling missing child case.

William was removed from his parents at the age of eight months and placed with the foster care family with whom he was living when he was abducted from the quiet cul-de-sac in Kendall while playing in the garden of his foster grandmother’s home.

There is no suggestion any member of William’s foster or biological family had anything to do with his disappearance­.

William would have celebrated his seventh birthday this month.

“William is constantly on my mind,” Brendan said.

“I don’t know if they’ll ever find him. I’m not sure I want to.”

William’s biological mother has previously told of her heartache over his mystery disappearance, saying: “Whoever has him needs a bullet.”

Addressing any abductor through Channel 7’s Sunday Night earlier this year, Karlie Tyrrell pleaded: “Don’t hurt him, let him come home.”

Fighting back tears, she said, “I’m coping as best I can,” revealing she split three years ago from Mr Collins, with whom she has three other children.

“I have a daughter … and my two younger boys … they’re not meant to be there to look after me.

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“I felt like the worst mum in the world when he disappeared, I just want this to end and William to come home.”

She said she had repeatedly searched her mind for clues to where he might be.

“It doesn’t make sense to me, kids just don’t go missing,” Ms Tyrrell said.

The foster parents say they, too, felt shocked and distressed since he vanished without a single trace.

William Tyrrell timeline

2014

SEPTEMBER 21 — Police stop searching for the missing boy after scouring surrounding bushland and neighbouring houses.

2015

JANUARY 20 — Police search the home and business of a washing machine repairman, who had been due to carry out repairs at the Kendall house at the time the boy disappeared.

JANUARY 23 — The washing machine repairman publicly denies any involvement in William’s disappearance and no charges have been laid against him.

FEBRUARY 19 — Homicide detectives take over the case and say it’s likely William was abducted.

MARCH 2 — Police search bushland near Bonny Hills for three days after a tip-off.

APRIL 17 — William’s foster parents speak publicly for the first time in an emotional video released through police which does not identify them.

APRIL 17 — Police say the boy may have been a victim of a paedophile ring.

SEPTEMBER 12 — “Where’s William” week is launched one year after he disappeared.

2016

SEPTEMBER 12 — A $1 million reward is offered for information leading to William’s return.

2017

AUGUST 24 — William’s foster child status is revealed after a court ruling.

2018

JUNE 12 — NSW Police announce the start of a four-week forensic search of bushland in Kendall.

Anyone with information on the whereabouts of William Tyrrell should contact Crime Stoppers on 1800 333 000