Four members of a family from Watford have gone on trial in connection with the theft of around three quarters of a million pounds worth of heavy plant machinery from construction sites across Hertfordshire.

The four were said to have been part of a gang that would target construction site vehicles like JCBs, which would then be sent to Eastern Europe.

On Tuesday a jury at St Albans Crown Court heard the thefts stretched from February 2011 to March of last year.

In the dock were Stacy Dunn, 36, of Cecil Street, Watford, his brother Lee Paul Dunn, 32, of Matlock Cressent, South Oxhey, and their father Lee Mark Dunn of High Street, Bedmond.

All three plead not guilty to conspiracy to steal heavy plant machinery between January 1 2011 and March 7 last year.

Also in the dock is Lucy Dunn, 32, who is Lee's wife also from Matlock Crescent, who pleads not guilty to two offences of transferring criminal property by paying £2,500 into her Barclays Bank account and later withdrawing the sum of £6,000 from the account.

Her husband denies a further charge of transferring criminal property by paying £3,700 into his wife's account at the start of his opening address to the jury; Simon Wilshire prosecuting said the case concerned the "systematic theft" of heavy plant machinery.

He said the police investigating the gang's activities had identified 17 actual thefts and he said the court would hear of two attempted thefts.

Mr Wilshire described the thefts as well planned and went on, "The evidence you will have to consider suggests plant and machinery was targeted and stolen with a view to exporting it to Eastern Europe."

He said it had been estimated that the value of machinery taken by the gang was between £700,000 to £800,000.

The jury were told at the centre of the gang was Stacy Dunn.

To give the court an example of how the thefts were carried out, Mr Wilshire said just before 5.10am on the morning of February 28 last year a JCB was stolen from a construction site in Bushey.

He said the thieves failed to locate a tracking device fitted to it and police were able to establish that around 30 minutes later it was inside a barn.

Mr Wilshire said police continued to monitor the JCB in the days that followed and then on March 5 last year it became apparent the JCB was on board a Polish articulated lorry travelling on the M25, bound for Dover.

The jury were told there was money to be made for the gang and some passed through the bank account of Lucy Dunn.

Mr Wilshire said three locations around Watford and Hemel Hempstead were used by the thieves to store heavy plant and machinery and change identifying features once they had been stolen.

One such place was Lower Little Heath Farm, Little Heath Lane in Potton End, between Hemel Hempstead and Berkhamsted.

Another spot was Fir Tree Farm in Shenley Lane, Radlett.

Mr Wilshire said a third location was Mentmore Boat Yard in Linslade, Leighton Buzzard.

Mr Wilshire said when a stolen vehicle was recovered from the Potton End storage site, police found a cigarette butt there which was found to contain the DNA of Lee Mark Dunn.

A contact phone number given by a man when booking a storage facility at Mentmore Boat Yard could be attributed to Lee Paul Dunn, said the prosecutor.

Keys to open padlocks at the site were later found by police in Lee Paul Dunn's VW car, the jury were told.

CCTV cameras also captured on film Stacy Dunn loading a stolen JCB onto a low loader at Fir Tree Farm, said Mr Wilshire.

The case continues.