Regina v The Princess. Defendant 2595640 is ordered to pay £500 over attack by bull terrier

Defendant 2595640, better known as the Princess Royal, barely whispered "guilty" as, at 10.02am yesterday, she became the first member of the Royal Family to become a convicted felon in 353 years.

Standing before a district judge in Slough magistrates' court, the Queen's daughter admitted to failing to keep one of her three English bull terriers under control when it attacked two boys in the shadow of Windsor Castle.

Fortunately, the penalty at stake in the case of Regina vs Anne Elizabeth Alice Laurence was not as serious as the last time one of her forebears was brought before English justice as a defendant. When Charles I was convicted of treason by a parliamentary tribunal in January 1649, he paid with his head.

Instead, the Princess found herself having to explain how Dotty, her three-year-old bull terrier, had left two boys bleeding and terrified in a flurry of gnashing teeth during an Easter Monday cycle ride.

Court 2, packed with journalists and subject to a super-tight security cordon, heard that Dotty – full name Dorothy – had as a result of the attack been defined as a dog "dangerously out of control" under the 1991 Dangerous Dogs Act, introduced after a serious of vicious attacks by aggressive canines during the late 1980s.

So it was that Mrs Laurence, of Gatcombe Park, Gloucestershire, found herself appearing in a court listing sandwiched between an alleged burglar from Reading and a man, 28, accused of illegally siphoning electricity.

For the defence team, the morning began well. An identical charge of allowing the dog to cause injury in a public place was dropped against the Princess's husband, Commodore Tim Laurence, or defendant 2595663.

The Princess, dressed in her trademark navy cardigan and high-collared blouse, was spared the necessity of sitting in the glass-panelled dock and remained instead by the side of her barrister. Her two children, Sara and Peter, were also in court.

The court then heard how the two victims – aged seven and 12 – had frozen in panic as Dotty suddenly sprinted away from her owner.

The Princess, 52, had been walking in a fenced-off section of Windsor Great Park with Commodore Laurence, 47, on 1 April – two days after the death of the Queen Mother – when the incident took place.

At about 3.40pm, the two cousins, who are Asian, had crested a hill in the company of the younger boy's father and two more of his nephews, only to find Dotty running at them from 150 metres away.

Anthony Smith, the Crown Prosecution Service solicitor, told the court: "The youngest boy came off his bike as the dog jumped up to him. The father arrived on the scene to find his son fighting off the dog. The father kicked the dog away from his son, who was trying to stand up. He kicked the dog away again."

The dog then turned its attentions to the older boy, who had ridden back when he heard the commotion and was again knocked to the ground amid a flurry of growls and scratches.

Mr Smith added: "The dog came back towards the boys on several occasions and was kept off them by the father. Commodore Laurence attempted to catch the dog but it ran off."

Dotty eventually ran back to the Princess, who set about locking Dotty in her car before she rushed to the aid of the two boys and their father. She packed up the bikes, washed their wounds and brought them back to their own car so they could be brought to hospital, the court heard.

As a result of the attack, the youngest boy suffered a puncture wound to his collar bone and two bites to his left thigh. The 12-year-old had scratches to his right forearm and the back of his left leg.

Both boys were left "traumatised" by the incident and deeply distrustful of all dogs, Mr Smith added as he submitted photographs of their injuries to District Judge Penelope Hewitt.

The court was told that the Princess was liable to six months in jail or a fine of up to £5,000. Dotty, like Charles Stuart, faced execution, albeit by lethal injection.

But the result was less severe. The dog was ordered to undergo retraining to cure its taste for chasing bikes and to wear a lead at all in times in public until it had done so.

Its owner was fined £500 and ordered to pay £250 compensation to each of the two boys as well as meeting prosecution costs of £148.

The reason for such enlightened justice, it seemed, had been a question of incisors.

Hugo Keith, for the Princess, told the court that a forensic dental surgeon, Luigi Caparelli, had examined the wounds inflicted by the dog and compared them with Dotty's jaws. The result, he said, was proof that Dotty had used her gentler incisor teeth, rather than her canines, to inflict the wounds on the boys. In a written statement, Mr Caparelli explained that the incisors were mostly used for harmless activities such as play, eating and removing parasites.

Seeking to distance Dotty from the predatory Rottweilers and pitbulls targeted by the Dangerous Dogs Act, Mr Keith said: "This case is quite unlike those notorious cases which have come before these courts in which children have been savagely attacked. The evidence points to Dotty having used her incisor teeth rather than having opened her mouth fully and using her aggressive canine teeth."

The court heard that a specialist dog psychologist, Dr Roger Monkford, had also spent two hours assessing Dotty and training her to leave bicycles alone by use of a remote-controlled device which shocks the dog with inert gas when it behaves wrongly.

All of which was enough to satisfy Mrs Hewitt that matters should be drawn to a close as she asked the Princess, if "you would be so kind", to stand up and face her sentence. She told the court that although the two boys had suffered a lot, Dotty's owners were "extremely responsible" and would adhere to the retraining order.

After the verdict, the families of the victims underlined the lingering effects of the attack on the two boys, saying they would have preferred to see the bull terrier destroyed.