Magistrates have convicted sole practitioner Robert Layton of assaulting his clerk for failing to photocopy court papers.
The clerk, who is now a freelance police station adviser, took out a private prosecution against his former boss.
Last week he told Haringey magistrates how, on 17 May this year, Layton, who is a partner at Layton & Co in Acton, shouted and swore at him and then struck him because he had not photocopied the papers.
Parkes said: "I pushed him back and said: 'Don't you touch me!'" Layton staggered back a few feet and then raised his right fist, he said. "It was like, 'Let's go!' It was a fight that was beginning."
Raymond Baretto, a solicitor at Layton's firm, told the court he stepped between the two because it looked as if Layton was about to punch Parkes. He said Layton "went into an absolute rage... He completely lost control. His face was red."
He added: "Bob was swearing and cursing, trying to get round him. He was growling and snarling, with both fists clenched, like he wanted to fight." After the incident Parkes said he went back to work and had a cigarette, but then decided to walk out. He walked straight to the police station.
Anthony Arlidge QC, defending Layton, told magistrates: "It's fairly extraordinary that we are all spending a large part of the day dealing with a fairly minor incident that might happen in many offices day in, day out."
Layton denied he had struck Parkes, saying it was a "reaching hold" to prevent him walking away. Layton, who had pleaded not guilty, was ordered to pay Parkes' costs of £785 and a further £20 in compensation for the shock caused to him but no other penalty was imposed on him.
Parkes has also complained to the Office for the Supervision of Solicitors, which is currently investigating Layton's behaviour.
One sanction available, if the case is referred to a disciplinary tribunal, would be to strike him off the Roll.
After the hearing Layton's counsel said he might appeal. Parkes said the Crown Prosecution Service had told him it would take up the case if it did go to appeal.
Parkes added that his two main witnesses worked for Layton and had not been willing to give statements to the police.
The CPS could not take up the case without witness statements. Parkes summonsed them so that they were compelled to give evidence.
Parkes said: "I'm quite happy with the result. All I wanted was him to have his day in court and to acknowledge the offence that he committed."