Three men were arrested last night in connection with the beating to death of a senior banker after he helped a homeless man who had been assaulted.

Frank McGarahan, 45, a married father-of-two who was chief operating officer of Barclays Wealth, was set upon by a group of around four men in Norwich at 3am on Sunday after remonstrating with the gang, police said.

Police said three men, who were all in their early twenties and from the Norwich area, had been arrested. A spokesman said the men were being held at police stations across Norfolk.

Mr McGarahan, of Much Hadham, Hertfordshire, had been queuing for a taxi with relatives at the time of the attack.

Detective superintendent Chris Hobley said Mr McGarahan witnessed an assault on a homeless Lithuanian man, in his late twenties, who was walking a dog with his girlfriend, from Norfolk.

Mr Hobley said there was an "exchange of words" and moments later the banker was set upon by the group of youths, aged between late teens and early twenties.

Mr McGarahan, along with his brother and cousin, were all caught up in the brawl.

The banker was knocked unconscious and taken to hospital with his cousin, who received less serious injuries.

Mr McGarahan did not regain consciousness following the incident and was pronounced dead at about 12.15pm on Monday.

Mr McGarahan was a frequent visitor to Scotland and had overseen the expansion of Barclays Wealth in Glasgow's International Financial Services District, Edinburgh and Aberdeen.

He had been photographed with former First Minister Jack McConnell at the Open at St Andrews and was well-known in Scottish financial and political circles.

It is understood Mr McGarahan was with one of his brothers, Kevin, at the time of the attack.

Police said Mr McGarahan, who had spent a "quiet night" enjoying a family meal and drinks at various bars, walked about 20 yards to the scene of the attack after witnessing it unfold from a taxi rank.

Police said they were following up "a number of very positive and encouraging lines of inquiry".

Tony McGarahan said relatives would never "truly recover" from the loss of his brother Frank. He added: "We will never understand how or why anyone could murder such a decent, caring and loving man. We will never comprehend it or truly recover from it."