Pre-tax profit at Persimmon, the FTSE 100 housebuilder, rose 16% to £271.5m in the first six months of the year, thanks to its acquisition of Westbury.

Turnover to the end of June rose 42% to £1.5bn. However the acquisition dented Persimmon’s operating margin, which was reduced from 23% to 19.9%.

Completions at the UK’s biggest housebuilder grew 38% to 8226 units, compared with 5954 units in the same period last year.

The company said the integration of Westbury was ahead of schedule, and that efficiency savings had reached £10m in the first half of the year, with a further £20m expected in the second half.

John White, group executive chairman, said: “Total sales revenues for the year so far, including completions, are at an all-time high of £2.9bn.

“The high level of sales already achieved puts us in a healthy position to achieve our volume expectations for the full year,” he added.

Persimmon rejigged its management structure after the enlargement. Mike Farley took over from White as group chief executive having been divisional chief executive of the original south division. Operations are now split into three divisions: central, north and south.

However there has been some fallout from the changes at the top. Westbury’s former finance director John Bennett is seeking £300,000 damages for breach of contract and unfair dismissal.