Patrick Bamford, a London-based Ulster fan, was left with a suspected fractured jaw after Brennan landed around a dozen blows to his face having launching himself into the crowd.

In unprecedented scenes, 33-year-old Brennan climbed into the stand, walked up six flights of steps and landed the blows after he had been enjoying some mild-mannered banter with the Ulster supporters while he warmed up in front of them in preparation to come on as a substitute during the second-half.

Eye witnesses claim that the only provocation from Bamford was a light-hearted dig at Brennan's Irish pub in Toulouse, which had been frequented by hundreds of Ulster supporters during the previous two nights.

After being hauled off, Bamford, who had to receive treatment from Ulster team doctor David Irwin, the former Ireland and British Lions star, Brennan returned to his dressing room and incredibly, moments later, was brought on as a sub in what was his last European Cup appearance for the French side.

Within minutes he had become involved in an ugly brawl with Ulster lock Justin Harrison, which saw both players shown yellow cards. Brennan did not return as Ulster, with their focus clearly lost by the incidents, went on to lose their final Heineken Cup game 28-13.

The ERC, the competition's governing body, has launched an investigation while Ulster Rugby have vowed to do all they can to help the inquiry. They are also set to cite Brennan for what Ulster coach Mark McCall described as an "assault" on Harrison.

"Ulster Rugby has made the organisers of the Heineken Cup, the ERC, aware of an off-the-field incident involving the Toulouse player Trevor Brennan," an Ulster Rugby spokeswoman said.

"During the match between Toulouse and Ulster in Toulouse, Brennan left the playing enclosure and physically assaulted a member of the Ulster travelling support. Ulster Rugby will be submitting a formal report to assist the ERC in their investigation of this serious matter."

An ERC spokesman said: "We are reviewing the incidents and are in the process of gathering information from both clubs."

Having made a verbal report to the ERC match official last night, Ulster Rugby will also be sending a written report on the incident.

Brennan will then undoubtedly face a charge of misconduct and appear before an independent disciplinary commission and the least he can expect is a lengthy suspension and possible life ban.

Toulouse could also be hit with a heavy fine while it is understood that Bamford, accompanied by a number of eye witnesses, also made an official complaint of assault to the French police before flying home.

Rugby chiefs must hit this idiot with a life ban Rugby chiefs must hit this idiot with a life ban

A massive dark cloud hung over rugby football today following the unbelievable scenes at Toulouse's Stade Ernest Wallon yesterday.

Rugby is a sport that has long prided itself on camaraderie between opposing supporters and complete absence of crowd trouble.

That reputation lies in tatters today following the vicious assault by Toulouse's former Leinster and Ireland forward Trevor Brennan on Ulster supporter Patrick Bamford.

For a professional player to wade into the crowd, and with a cool ruthlessness pick out his victim and unleash a barrage of blows to his face simply beggars belief. It was even worse than Eric Cantona's infamous lunge at Selhurst Park.

Only moments earlier, Brennan had been enjoying a bit of banter with the Ulster supporters as he warmed up behind the posts to come on as a second half substitute.

Then, from nowhere, the red mist came down.

When Brennan jumped into the stand and climbed the steps, it had the hallmarks of a pantomime scene. Bamford even held out his hand to shake Brennan's.

As he sat in his seat wearing a Santa hat, he could not have imagined that he was about to be subject to a vicious assault.

No provocation warrants such an assault and it is understood the only jibe Bamford made was to have a dig at Brennan's Irish pub in Toulouse, an establishment that many Ulster fans had frequented over the previous two nights.

Moments later Brennan was allowed to take the field of play, only to become involved in an ugly brawl with Ulster's Justin Harrison and receive a yellow card.

There is no place for such actions in any sport, or indeed any walk of life. The rugby authorities must act swiftly and harshly to send out an unequivocal message. Brennan must receive a life ban from rugby and Toulouse should terminate his contract. The ERC should also hit Toulouse with a heavy fine. A dark day indeed.