The decade-long investigation into the £5m construction  tax fraud ended this week with prison sentences issued to gang leaders 58-year-old Francis Devlin and 56-year-old Paul McStravick for a combined total of eight years.

HM Revenue and Customs (HMRC) mounted its biggest ever operation in Northern Ireland to bring the 27-strong gang to justice.

The case was based on more than 260 hours of secretly recorded footage of gang members plotting the fraud from the Belfast accountancy firm Allen Tully & Co where Devlin was a partner and the wider gang used as a base.

The gang created a false audit trail that enabled clients to operate in the construction industry without paying tax or VAT.

They created 16 bogus companies and used 56 associated bank accounts to commit the fraud.

Working with partners in the PSNI, the Public Prosecution Service (PPS), the National Crime Agency and financial institutions, HMRC built the case before swooping on 34 premises.

More than 400 HMRC officers searched 34 business and residential premises in March 2012, including three in England, in its biggest ever operation in Northern Ireland.

HMRC kept the gang under the secret surveillance for six weeks between February and March 2012.

Devlin and McStravick were jailed for four years each. Another 25 accomplices, most of whom knowingly allowed their personal details to be used as part of the fraud, were handed suspended prison sentences.

Richard Las, Director, Fraud Investigation Service, HMRC, said: “This was a sophisticated and complex fraud that took the largest ever tax probe in Northern Ireland, including extensive covert surveillance, for HMRC fraud investigators to bring it down.

“Their tenacity and expertise has stopped the loss of millions of pounds in taxpayers’ money, which is now paying for our vital public services, rather than lining the pockets of criminals.

“The fact is, no tax criminal is beyond our reach and that includes those corrupt professionals who aid and abet them, as these sentences clearly show.”