A retired accountant handed over his savings and had to re-mortgage his Watford home after being tricked by conmen builders, a jury heard on Friday.

Yiu-Wing Au, 68, paid almost £100,000 for work on his Cassiobury Park Avenue house that was of such a poor standard that it should only have cost £8,746, St Albans crown court was told.

Prosecutor Ann Evans said: "Mr Yiu-Wing Au, who likes to be called Wing, lived on his own in Watford. He has never married and has no children. His mortgage was paid off several years ago and he had amassed quite a lot of savings.

"He could look forward to a comfortable retirement, until one day in August 2011 two strangers knocked on his door and told him his roof was in need of repair.

"As a result of this knock on the door, and the trust he put in these strangers, he also became deeply indebted by re-mortgaging his house. The only reason he parted with this money to these fraudsters was because of the lies and threats made to him.

"If it wasn't for good friends around him, it seems this matter may never have been reported to the police. It came to light only as a result of one of his friends reporting her suspicions to the police after Wing had phoned her up asking to borrow £45,000."

Six men went on trial at St Albans crown court. They are: James O'Brien, 49, of Chauncy House, Croxley View, Watford; Michael O'Brien, 37, of Russells Ride, Cheshunt; Nathan Newman, 33, of Twyn Carmel, Merthyr Tydfil; Paul Watkins, 37, of Kemp Road, Enfield; Darren O'Driscoll, 21, of Purkiss Road, Hertford and Patrick O'Driscoll, 34, also of Purkiss Road, Hertford.

Michael O'Brien, James O'Brien, Nathan Newman and Paul Watkins deny conspiracy to commit fraud.

Michael O'Brien, Patrick O'Driscoll and Darren O'Driscoll deny conspiracy to commit fraud.

The prosecutor said Mr Au was approached by two men - alleged to be brothers Michael and James O'Brien - to say work needed to be done on his roof.

Ms Evans said: "Work was carried out between August and December 2011. By that time he had parted with nearly £100,000.

"Whatever work had been done was to such a poor standard as to cause condensation, with items coming loose and falling off the roof.

"Wing called Michael O'Brien who said he was in Ireland, but told Wing not to worry as everything was under guarantee and an associate who was working in Watford would come and sort out the problems.

"Patrick O'Driscoll then arrived and claimed the whole roof may fall down. Mr Au is told to pay Mr O'Driscoll further money which will be reimbursed by Mr O'Brien - it never was."

She alleged that Michael and Jimmy O'Brien never did any of the work carried out between August and December 2011. Among those she said that did the work were: Nathan Newman and Paul Watkins.

It was said that Patrick O'Driscoll did some work on the roof after Wing had contacted Michael O'Brien. His brother Darren O'Driscoll is said to have come to the house to pick up money - not doing any work himself.

The jury of 10 men and two women were told that a member of the Chartered Institute of Building was to carry out an inspection of the work at Wing's home. The inspector said that the standard of the work carried out was worth £8,746, which was £90,000 less than was actually taken.

Mrs Evans said that Mrs Bianca Wong, a friend of Wing, contacted the police after he had rung her to ask her to lend him £45,000. "She was shocked knowing that he was a qualified accountant and believed him to be comfortably off.

"She and two others from the Chinese community went to visit Wing the following day. He told them that he had a problem with some builders."

Case proceeding