Bosses at British security giant G4S, which guards sites including prisons, offices and COVID test-centres, on Wednesday backed a £3.8-billion takeover from US rival Allied Universal that trumps a bid from Canada’s GardaWorld.

G4S announced in a statement posted on the London Stock Exchange that its board was “unanimously recommending” Allied’s new offer, worth the equivalent of $5.1 billion or 4.2 billion euros, after concluding that 245 pence per share was “fair and reasonable”.

The UK security titan, which in recent years has been caught up in scandals across the world, added that it has rejected GardaWorld’s improved £3.7-billion bid which lodged last week and was pitched at 235 pence per share.

The combined company will have total revenues of around $18 billion with a “world-leading” integrated security business and a strong international platform.

“The combination of G4S and Allied Universal creates the global leader in security with over 750,000 employees, industry leading capabilities and unrivalled market coverage,” said G4S Chief Executive Ashley Almanza in the statement.

“This unique and compelling combination will offer customers exceptional service and provides employees with an exciting future.”

The London-listed company had already turned down a £3.25-billion proposal from Allied in early November, arguing that this conditional approach had undervalued its prospects.

Steve Jones, president and chief executive of Allied Universal, added on Wednesday that the group was “delighted” to win the board’s recommendation.

“Our businesses know each other well, we share a similar culture and values and I am excited about what the combination of Allied Universal and G4S can deliver,” he said.

“G4S has an excellent service offering, an enviable global customer portfolio and it is led by a highly experienced management team.”

G4S, which itself employs 533,000 staff across 85 countries, had faced a takeover tussle between Allied and GardaWorld with both suitors pledging to vastly improve its tarnished image.

While mostly linked to allegations of mistreatment by staff in the UK, the company has been accused also of mismanagement at the US military’s Guantanamo prison camp and in the West Bank.

The company has become an attractive buying opportunity after its share price hit a 16-year low earlier this year.