The former chief constable of South Yorkshire police said he had not believed the evidence against Sir Cliff Richard “to be particularly strong” when his force raided the singer’s home after an accusation of historic sexual assault.

David Crompton told the high court in London he was not personally involved in the case but had been informed by officers that they were “unsure whether the investigation would lead to charges”.

Richard, 77, is suing the BBC for substantial damages, arguing that the broadcaster infringed his right to privacy when it used a helicopter to film officers raiding his Berkshire home in August 2014.

The singer strongly denied the accusation that he assaulted a boy after an event in Sheffield during the mid-1980s, and no charges were ever brought. South Yorkshire police have already paid £400,000 to the singer after the incident.

Compton told the court on Wednesday that he was shocked when he was informed by the force’s press officer that a BBC journalist, Dan Johnson, had been in touch about the nascent investigation in July 2014. The police press officer claimed Johnson had said he was ready to publish a story on the investigation.

“I can remember very clearly thinking there was a journalist who knew as much as I did about the allegations,” Crompton said. “This information was deeply concerning to me because I thought that a media report on a high-profile case, which was in its infancy, could fatally compromise [South Yorkshire police’s] ability to carry out a thorough investigation.”

As a result the decision was taken to cooperate with the BBC and tell the broadcaster when a raid would take place, the court heard.

Crompton told the court that when he finally saw helicopter footage of the raid he thought it was “intrusive” and swiftly texted a colleague asking him to be careful about what iwas “said on email” about the case because he was concerned about a freedom of information request.

Earlier on Wednesday, Fran Unsworth, who is now the BBC’s director of news and current affairs, told the court it was the right decision to press ahead with the coverage.

“I took the view, and still do, that we had a responsibility in the public interest, this whilst being sensitive to the position of Sir Cliff,” she said. “The BBC has publicly said it is very sorry that Sir Cliff has suffered distress and that remains the position.”

She also said it was correct for the broadcaster to use helicopter footage of the singer’s home. “They did not show anything which I would describe as personal or intrusive and [it] lasted a few seconds.”

Unsworth was also questioned on why the BBC decided to submit the story for “scoop of the year” in the Royal Television Society’s annual broadcast news awards, a decision she said had sent the wrong signals.

The case continues.