The move by Giuliani to appear before the panel – in a cooperation deal that could be agreed within weeks, according to two sources briefed on negotiations – could mark a breakthrough moment for the inquiry as it seeks to interview key members of Trump’s inner circle.

That is the case because even though Trump’s allies and Republican members of Congress already known to have been involved in such efforts have refused to help the panel, Giuliani is now in a position to inform House investigators about any possible culpability.

Broadly, Giuliani has indicated through his lawyer to the select committee that he will produce documents and answer questions about Trump’s schemes to return himself to office on 6 January that House investigators had outlined in a subpoena issued to him last month.

The former president’s attorney is prepared to reveal his contacts and the roles played by Republican members of Congress in the scheme Giuliani helped orchestrate to have then-vice-president Mike Pence stop the certification of Joe Biden’s election victory.