Birse Chief executive Peter Watson said he was “astonished” after his company was awarded only £500 000 in its long-running dispute with Caerphilly council. The firm had expected to be awarded £8.1m from the case.

The court battle over payment on the Rymney Valley Relief Road project began four years after the project was completed in 1992. But Birse made national headlines – and bewildered the industry – when its negotiations with Caerphilly officials descended into farce.

In 1998, the firm sent council chief executive Malgwyn Davies gifts of crystals and fairies and employees dressed as animals demonstrated outside council offices as part of its reinvention from hard-nosed operator to caring contractor.

Birse has acknowledged that a “significant” asset write-off will have to be made to cover the loss. “We were advised to expect the figure akin to what we had in our books, so it was a great surprise,” said Watson. “But we have structured our business to be able to carry out work without these receipts.”

Sources said that Birse’s claim was closer to £14m, including its costs at about £5m, plus £4m for the council’s costs, plus interest. Birse is expected to decide on an appeal next week.