Investigations into a crash linked to a car carrying Australia’s former UK high commissioner George Brandis have cost taxpayers more than $250,000.

Australian officials disclosed the costs of two external investigations on Thursday, while also revealing Surrey and Sussex police had sought an additional $26,320 from Australia to cover the damage sustained by two of their vehicles in the crash.

The Australian diplomatic vehicle carrying Brandis was not damaged in the incident, which happened at the time of the Cop26 climate summit in November 2021.

Sydney’s Daily Telegraph reported that Brandis’s vehicle was trying to catch up with then prime minister Scott Morrison’s motorcade on the way to a stakeholder breakfast when security officers in two Metropolitan police cars “took defensive measures to head off the perceived threat”.

Brandis, a former Coalition government attorney general prior to his diplomatic appointment, was not the driver.

Australia’s Department of Foreign Affairs and Trade commissioned two investigations into the incident, the first of which had a more limited scope and was carried out by Simon Devonshire KC at a cost of $11,530.

“Mr Devonshire’s role was to advise whether any disciplinary action should be taken against the driver of the vehicle,” the department’s chief operating officer, Clare Walsh, told a Senate estimates committee hearing.

“He did not recommend any disciplinary action against the driver.”

Walsh said the first investigation had been commissioned by Australia’s high commission in London.

The then secretary of Dfat, Kathryn Campbell, requested a second investigation because “she wanted something that was arm’s length” of the high commission, Walsh said.

The law firm Ashurst London signed the contract in February and provided a report in July after interviewing 12 staff from the Australian high commission, including Brandis.

Walsh said the second investigation cost $240,000 and focused on work health and safety issues associated with the incident.

She said it had found that the high commissioner’s transport was “not in accordance with scheduled arrangements”; a bus had been organised to take members of the Australian delegation to a breakfast.

“Ashurst found that while the high commissioner was scheduled to take the bus on that day, the advice to him about changing the arrangement was made very late in the evening and was probably not effectively communicated to either himself or a member of his team,” Walsh said.

“That report also didn’t recommend there be any conduct action against any individuals involved in the matter.”

Surrey and Sussex police submitted a request in August for $26,320 to cover the damage to their two vehicles. This had been referred to Comcover, the Australian government’s insurance fund, which was still considering the claim.

Walsh said the matter was “now considered closed” and the UK authorities were “not intending to pursue the matter further”.

She said the department had developed an action plan to learn lessons from the incident.

The Labor senator Linda White, who led questioning on the issue, said it had been “a pretty expensive process for the department” and added: “Surely one of the lessons would have been to take the bus.”

White asked about media reports suggesting the driver had been required to work late the night before the incident and had then been required to start early.

Officials confirmed that Ashurst had examined the rostering of drivers.

The Dfat secretary, Jan Adams, said the rostering of staff “in these very intense international conference environments or big visits” should take into account work health and safety obligations.

Brandis, who is now a professor at the Australian National University, told Guardian Australia on Thursday: “I have not seen the report but I understand it contains no findings adverse to me and that some earlier media reports have been shown to be false by the inquiry’s findings.”