Harris was wide open to any legal action for defamation and in my view City would have won any case. Introducing defamatory information in the form of a question makes no difference. The allegation was broadcast on TV and re-published on websites.
The media have some legal protection from information they mention during any press conference known as Qualified Privilege but to use this defence they would have to show they had been fair, balanced, and accurate in their coverage and Harris has done none of this. If we had sued him he would have to prove what he alleged is true. He made it worse by repeating it online after the conference.
For example if a journalist randomly asked someone at a public press conference: "What's your reaction to being called a paedophile," they would be open to an action for defamation and they would require strong evidence to support their allegation in any subsequent civil action.
To accuse Pep of being a criminal (tax evasion) is almost as bad as it gets for a public figure. What Harris did was reckless and unprofessional and would have cost him his job in many media organisations.
I have no idea whey City let this one lie or why Hariss's employers, the AP agency, did not take action against him.