"He set down the water, called me another name, then came at me. It all happened so fast. So very fast. He grabbed me by the collar, ripping my necklace..."

"... and he knocked me to the floor. I landed on the dog’s bowl, which cracked under my back, the pieces cutting into me. I lay there for a moment, dazed, then got to my feet and told him to get out."

Writes Prince Harry, quoted in "William is my ‘arch-nemesis’, says Harry in new book Spare" (London Times). 

William, according to Harry, urged his little brother to hit him back, recalling the fights they had as children. Harry, however, said he refused and William left before returning, “looking regretful, and apologised.”

When William left again, Harry said he “turned and called back: ‘You don’t need to tell Meg about this.’

“‘You mean that you attacked me?’

“‘I didn’t attack you, Harold.’”

Harry said he did not initially tell his wife but called his therapist. Meghan, 41, is said to have later spotted “scrapes and bruises” on Harry’s back and it was then that he told her about the attack. Meghan, according to Harry, “wasn’t that surprised, and wasn’t all that angry. She was terribly sad.”

Elsewhere in the London Times, in "Harry’s book Spare is excruciating in its detail of fight with William/Claim that prince knocked his brother to the floor takes things to a new level," Valentine Low writes:

That William — like his father — has a temper is well known. But the claim that he would grab his brother by the collar and knock him to the floor takes things to a new level. It will also be an accusation that William will find hard to shake off: he will always be the prince who attacked his brother.