The judge, referring to a statement from the boy victim, told Reading Crown Court: 'The defendant required him take work to his desk. He was asked questions. Then it was alleged he placed his hand on [the victim's] neck and ran it down his back and patted his backside.
"It would remain there while he was questioned by the teacher."
Speaking of the showers incidents at the school, the judge continued: "The victim says Mr Brailsford was the only teacher who did this to him and other boys."
The victim, who was aged 12 or 13 years old and was boarding at the school at the time, told police in 2014 that he was attacked between five and seven times.
The court heard the victim also said that Brailsford had watched him showering with other naked boys at the school.
The jury was discharged from the court after Mr Recorder Christopher Quinlan QC ruled that they should hear that Brailsford was warned by the schoolmaster Reverend Roger Marsh over him touching boys sexually at the school.
'Another set of parents told Reverend Marsh of rumours about the defendant's behaviour,' the judge said.
Mr Recorder Quinlan said jurors would be told about the headmaster's note of a meeting he held with Brailsford following a verbal warning over his behaviour.
The note, which was kept in the school's records and supported by a later statement from the Reverend Marsh, read: 'I saw the senior master in connection with allegations made about him, touching boys on the back and bottom.
"Mr Brailsford said that he did sometimes run his hand down backs of boys in that way."
The court heard that the Reverend Marsh warned Brailsford verbally about the assaults after the boy, who had been preparing for entrance exams to join prestigious Eton College, had left the school.
The judge said Brailsford had 'assured' the Reverend that the attacks would stop at the meeting in April 1998.
The headmaster's note continued: "He said it still happened but less often, despite the verbal warning I gave him on April 7, 1998."
The court heard that the Reverend Marsh, who had also spoken to Brailsford over the rumours two months before the formal warning, later sent a further written warning to the teacher.
The judge said social services then launched an investigation and police were informed.
He ruled the jury could hear of Brailsford's admissions of having indecent images after his defending lawyer, Jon Mitchell, told the court they were 'naturist' and not of a sexual nature.
The court heard they included an image of of Michaelangelo's world famous Statue of David.
However, Mr Recorder Quinlan said: "The defence do not accept that it shows a sexual interest in boys or at all... being naturist in nature, they depict no sexual acts.
"It is right also that there is the occasional naked statue. There might well have been a single image of Michaelangelo's David."
But he added there were also hundreds of images of which the majority were of 'pre-pubescent boys' naked backsides'.
The hearing was adjourned temporarily as the prosecutor Jane Davies and Mr Mitchell agreed for the defendant, who lives in Windsor, to change his pleas and to admit the charges.
Mr Recorder Quinlan told the jury: "He having admitted those charges, your work done, so I am going to formally discharge you from delivering a verdict."
Brailsford, who appeared in the dock dressed in a dark suit and blue tie, was released on conditional bail to return to the court to be sentenced on January 6.
The teacher, who had admitted the indecent images charges last April, was ordered not to enter St George's School or its grounds.
Brailsford was also forbidden from making direct or indirect contact with anyone involved in the case and from having any unsupervised contact with anyone under the age of 16 years.
He must also live and sleep each night at his home address and co-operate with the probation service which will prepare a pre-sentence report on him before his sentencing in January.
At the time the offences were claimed to have been committed, Brailsford was a schoolmaster at St George's, having been appointed as acting headmaster in 1993.
Pupils who attend the school, which is a unisex day and boarding school for those aged three years to 13 years, include the choristers of St George's chapel - a place of royal worship situated behind the school in the grounds of Windsor Castle.
