Bulmers has increased security at its cidermaking plant after the conviction of a man for attempting to contaminate its production line.

The firm behind the Strongbow and Scrumpy Jack brands said it had reviewed procedures after the conspiracy had been discovered.

The failed attempt at contamination ended with Michael Hancocks, a major shareholder of rival firm Aston Manor Brewery, being jailed for 18 months.

Bulmers PR manager George Thomas said the trade had no cause for concern.

“As a result of the incident two years ago we have imposed even stricter security. Quality remains at the highest possible standard.”

The plot was the result of a bitter feud between Aston Manor and Bulmers, which dates back to 2001 when both companies were competing for a supply contract with Booker.

Bulmers went on to win the most profitable part, prompting Hancocks, from Hereford, to devise a plot to contaminate the production line with a yeast-based bacteria.

The plot failed after the Bulmers factory worker recruited to administer the contaminate informed his line manager who then called in police.