Apparently, Harwood has form...

From the Wikipedia article on Ian Tomlinson

The officer seen striking Tomlinson was a police constable with the Territorial Support Group (TSG) at Larkhall Lane police station in Lambeth, South London. Before his identity was known, The Guardian alleged that he may have removed his shoulder number and covered the bottom of his face with his balaclava before hitting Tomlinson. The Daily Mail published this image showing the officer's shoulder ID was missing. According to The Mail on Sunday, TSG officers have been known to swap shoulder IDs, then claim, if accused of wrongdoing, that their unit was elsewhere at the time and that it must be a case of mistaken identity.
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Harwood had faced two misconduct hearings in the late 1990s and in 2004. The first arose out of a road-rage incident while he was on sick leave with a shoulder injury, during which he reportedly tried to arrest the other driver, who complained that Harwood had used unnecessary force. Before the case was heard, Harwood retired from the Met on medical grounds and was awarded a pension. Three days later, he rejoined the Met as a civilian computer worker.

Several years later, he applied to join the Surrey Police as an officer; Surrey Police say he was vetted and was frank about his history. During his time in Surrey, there was a complaint about his behaviour while on duty; it was investigated and found to be unsubstantiated. After working there for 18 months, he applied for a transfer back to the Met as a police officer, and was accepted in November 2004. It is not clear how thoroughly the Met vetted him at that point.

During the inquest into Tomlinson's death in May 2011, the court heard that Harwood had been in several confrontations that day. On duty since 5 am, he had tried in the evening to arrest a man he saw writing "all cops are bastards" on the side of a police van, and the suspect's head struck the van door, triggering a response from the crowd that made Harwood believe things were getting out of control. He apparently said he had been hit on the head, had fallen over, lost his baton, and had been attacked by the crowd. He acknowledged during the inquest that this had not happened. Shortly after his attempted arrest of the graffiti man, The Guardian wrote that Harwood swung a coat at a protester, pulled a BBC cameraman to the ground, used a palm strike against a city worker, and at 7:19 pm pushed another man to the ground for allegedly threatening a police dog handler. It was seconds after this, in what Harwood told the inquest was a "split-second decision," that he struck Tomlinson on the thigh with his baton and pushed him to the ground. He said that it was a "very poor push," and he had been shocked that Tomlinson had fallen.

Harwood made no mention of the incident in his notebook that day; he told the inquest he had forgotten about it. He reportedly collapsed when he learned on 8 April, when The Guardian published the video, that the man he hit had died. Harwood and three colleagues made themselves known to a manager and to the IPCC that day.

(Note: emphasis (i.e. bf) added by me)