Media playback is unsupported on your device Media caption FBI's Peter Strzok: Anti-Trump bias claims 'deeply destructive'

President Donald Trump may be out of the country, but Robert Mueller's investigation into possible ties between the Trump campaign and Russia grinds on. And Thursday was a fairly dramatic day on multiple fronts.

At the US Capitol, one of the former top members of the special counsel team, FBI agent Peter Strzok, was grilled by members of Congress over allegations of bias revealed in a series of text messages he exchanged with Lisa Page, a fellow FBI employee with whom he was having an affair.

Although the president had just concluded a long day of meetings at the Nato summit in Brussels, his mind was clearly on Washington, as he tweeted about the "Rigged Witch Hunt" and Mr Strzok's "hate filled and totally biased Emails" just before 01:00 local time.

Mr Strzok, a senior FBI counterintelligence agent who has spent much of his career hunting down Russian spies in the US, was dismissed by Mr Mueller last summer after he learned of the messages, which included disparaging comments about then-candidate Trump and his supporters (as well as Obama Justice Department officials and other Democratic and Republican politicians).

Media playback is unsupported on your device Media caption Republican Louie Gohmert asked Peter Strzok how many times he lied to his wife

In addition to his involvement in the Trump-Russia investigation from its early stages, Mr Strzok was also a key figure in the FBI review of Hillary Clinton's handling of classified material on her personal email server while she was secretary of state.

In one particularly testy exchange, Trey Gowdy of South Carolina questioned Mr Strzok about messages in which he said "we'll stop" Mr Trump's election and that Democrat Hillary Clinton should win 100m votes to zero.

After Mr Strzok said he'd appreciate the chance to explain, the chair of the House Government Oversight Committee shot back: "I don't give a damn what you appreciate, agent Strzok. I don't appreciate having an FBI agent with an unprecedented level of animus working on two major investigations in 2016."

That set up perhaps the most pivotal moment of the ongoing hearing, as Mr Strzok attempted to defend his, and the FBI's, integrity and explained that the texts in questions came after Mr Trump insulted the Muslim parents of a slain US soldier.

At the end of his monologue, Democrats in the committee chamber applauded.

The rest of the proceedings were frequently bogged down in parliamentary manoeuvring, with a few nuggets of information mixed in. Mr Strzok would note at one point that information about a Russian offer to help the Trump campaign was of "extraordinary significance" and came from an "extraordinarily sensitive and credible source". The hearings were burdened, however, by a queue of more than 70 members of Congress waiting to ask questions.

If the Gowdy-Strzok exchange were the Fourth of July fireworks, the rest of the day was the traffic jam as the crowds stuck in their cars tried to get home.

Image copyright Getty Images Image caption Peter Strzok calls allegations of FBI bias and misdeeds "deeply destructive"

A reversal of fortune

Meanwhile, across the Potomac River in Alexandria, Virginia, former Trump campaign chair Paul Manafort arrived at his new jail facility, as he awaits the first of two trials on charges of money laundering, illegal foreign lobbying and obstruction of justice.

Although the charges are unrelated to Mr Manafort's work for candidate Trump, Mr Mueller's team is vigorously pursuing the case - perhaps in the hope of eventually gaining the long-time Washington insider's co-operation in his ongoing investigation.

Image copyright Getty Images Image caption Former Trump campaign chair Paul Manafort's time in jail appears to have taken a toll.

They had sought, and secured, Mr Manafort's pre-trial incarceration in early June, after presenting evidence to one of the presiding judges that he had reached out to possible witnesses in his case in an attempt to influence their testimony.

A mugshot from Thursday morning revealed a somewhat beleaguered Manafort - who used to sport well-coiffed hair and Italian suits - in need of a shave and a haircut after more than a month in jail.

Mr Manafort's lawyers had been asking to have his 25 July trail date pushed back to allow him more time to prepare - a request that the judge recently denied.

Mr Mueller, who has been on the job for 14 months, has been Sphynx-like in his silence. The only public voice he has had so far is through its court filings. In fact, he's been so scarce in the public's view that most media outlets are running the same series of photographs taken as he walked the halls of the US Capitol back in June 2017.

In two weeks, the special counsel's team will appear for the first time in a jury trial. The stakes will be high, and the spotlight's glare will be the brightest it has been so far.