Colin Firth's wife Livia Giuggioli (pictured in London last December) has admitted having an affair with a friend she accused of stalking

Colin and Livia Firth appeared together on the red carpet numerous times during the period they said they were 'briefly separated', it emerged today.

The couple seemed determined to put a brave face on their relationship woes as they posed for the cameras at the Baftas in February 2016 and a host of other red carpet engagements.

They appeared at London Fashion Week together in September 2015, the relaunch of the Great Gallery in London that same month and the premiere of Nocturnal Animals in the summer of 2016.

Mrs Firth, 48, is understood to have been having an affair with Italian journalist Marco Brancaccia, 55, as she posed arm-in-arm with her husband.

She sparked a police investigation after claiming her childhood friend Mr Brancaccia harassed her with a 'frightening' barrage of messages.

Today, sources said Firth confronted his wife with a 'heartbreaking and malicious' email from her ex-lover as he struggled to save their marriage.

The Mercy actor sat down his mortified spouse of 20 years in tearful crisis talks 18 months ago.

Oscar winner Firth had received a 'detailed diatribe' of his wife's one year relationship with jealous Mr Brancaccia on his personal email. Mrs Firth had dumped the journalist to be reunited with Firth.

The message contained revelations 'designed to wound' the King's Speech star - who has maintained a dignified silence over the affair. It is the first time details of its content have emerged.

A friend of Firth's said: 'This guy Marco basically told Colin everything he had been doing with his wife for a year. The email was a detailed diatribe, humiliated Colin and was designed with no other motive than to wound.

The couple seemed determined to put a brave face on their relationship woes as they posed for the cameras at the Baftas in February 2016 (above) and a host of other red carpet events

In September 2015, when the couple were said to be separated, they appeared at the Sergio Rossi green carpet collection and also at the Vanity Fair Oscar party in February 2016

They also made a joint appearance at the Cannes Film Festival in May 2016 and the Venice film festival in September 2016

'He described intimate meetings that would devastate any husband – no matter what the state of their marriage. And he did so with the misguided and hopeless belief he could destabilise the efforts being made by Colin and Livia to sort things out.

'Colin presented this to his wife and in what must have been a very difficult confrontation. But he is the man that he is and has maintained his dignity throughout.'

Italian prosecutors were alerted over the email and Mr Brancaccia is being investigated by police. Details of law involvement first appeared in Italian newspaper La Repubblica.

A spokesman for Italy's Carabinieri police said: 'A complaint has been made by the couple to prosecutors and the police have been investigating.'

Mrs Firth, 48, admitted Mr Brancaccia's affair happened during a trial separation by the Firths. However, they have put up a united front throughout the alleged stalking campaign.

The source said while the marriage had been 'strained', they believed no third party had been involved prior to Mr Brancaccia.

They said: 'Colin is one of the biggest movie stars in the world and Livia also travels extensively with her producing work and charity campaigning.

Firth, pictured with Livia, holds the Oscar he won for The King's Speech in February 2011

'It's easy to forget they also have two teenage sons and are human. Cracks can appear and things become strained and this is what happened in this case.

'No one else was involved. They are still working at things but are determined to remain together.'

As well as the email to Firth, his wife claims she received phone calls, lived in terror and believed she was being followed.

Livia Giuggioli, 48, alleges Marco Brancaccia threatened her through telephone calls and texts

Mrs Firth said her former lover began threatening her with telephone calls and texts after she had reunited with her 57-year-old husband.

Mr Brancaccia, 55, told The Times that Mrs Firth had invented the claims to cover up their affair, which happened between 2015 and 2016.

The Firths, who have been married for 20 years, have two sons, Luca, 16, and Matteo, 13. They live in Chiswick in west London, but own a house near the community of Città della Pieve in Umbria.

A spokesman for the couple said: 'A few years ago Colin and Livia privately made the decision to separate. During that time Livia briefly became involved with former friend Mr Brancaccia. The Firths have since reunited.

'Subsequently, Mr Brancaccia carried out a frightening campaign of harassment over several months, much of which is documented. For obvious reasons, the Firths have never had any desire to make this matter public.'

Details of the police probe first appeared in Italian newspaper La Repubblica.

It reported that Mr Brancaccia began stalking Mrs Firth in September 2016 because he could not face being cut out of her life.

He is accused of threatening to write compromising articles about her and Firth before emailing photographs to the British actor, prompting him to alert Italian prosecutors.

In the complaint, Mrs Firth said she was living in terror and thought Mr Brancaccia might be following her, the newspaper said.

The journalist, who works for the Italian news agency Ansa, said the stalking allegations were false.

'We were romantically involved, she wanted to leave Colin for me,' he said, claiming that Mrs Firth's marriage to Firth had 'been over for years'.

'My 'stalking' consisted of two messages via [the messaging service] WhatsApp after she ended our relationship in June 2016, and an email,' he said.

Mrs Firth (pictured with Firth in 2014) is an Oxfam ambassador and has travelled to Ethiopia, Kenya, Bangladesh and Zambia

'I wrote an email to Colin about my relationship with Livia, which I now regret sending, and she filed a complaint against me for stalking out of fear that I could go public with what she had revealed to me about her marriage and work,' he said.

'In a year she sent me hundreds of messages of love, photos and videos, even a diary,' he added. He regretted involving Firth, who he said had shown 'understanding'.

Ansa said Mr Brancaccia remained an employee. He has worked for the firm since 1988 and is based in Brazil as its bureau chief, according to colleagues.

Italy introduced a law against stalking in 2009 following an increase in women being harassed and murdered, sometimes by former partners.

If found guilty, Mr Brancaccia could face up to four years in jail. His lawyers say he had 'absolutely nothing to do with the events described and has already filed a legal complaint to protect his good name and his honour'.

On top of her work as a producer, Mrs Firth is an Oxfam ambassador and has travelled to Ethiopia, Kenya, Bangladesh and Zambia.

The mother of two is also a founding member of The Circle, a women's advocacy group set up by singer Annie Lennox. She also founded Eco-Age, a consultancy that advises fashion companies on environmental sustainability.

Her husband thanked her 'for putting up with my fleeting delusions of royalty' in his Oscar acceptance speech for his role as King George VI in 2010 film The King's Speech.

Firth began to learn Italian after he started courting Livia and speaks the language fluently. He applied for citizenship of the country after describing Brexit as a 'disaster' in an interview with an Austrian newspaper in 2016.

He said: 'For me this is a disaster of unexpected proportions. Brexit does not have a single positive aspect.