It may be almost 50km from Dublin’s south inner city to Delgany, Co Wicklow, but the Garda Armed Support Unit’s (ASU) Audi Q7 Quattro makes light work of the journey.

The vehicle can travel at speeds of up to 250km/h and the vehicle’s blue lights and sirens ensure a path is cleared through the traffic.

A report has come in over the radio of a powerful machine-gun-type firearm being transferred from one vehicle to another. Local gardaí have traced the owner of one of the cars to an address in Delgany. The ASU is alerted.

Gardaí are keeping eyes on the house but, because of fears the occupant has a powerful firearm, it’s a job for the armed members of the ASU.

Two members arrive at the address and immediately get to work. They are each armed with a Heckler & Koch MP7 submachine gun – also used by the State’s Army Ranger Wing and the British army’s SAS – and a Sig Sauer 9mm pistol. They also carry a range of less than lethal options, from a Taser stun gun to rounds loaded with pepper spray and rubber-bullet-type rounds.

On Wednesday night in Delgany there is no need for the ASU’s capacity for force, either lethal or less than lethal.

The eastern European man who answers the door to the ASU is initially surprised to see them, but then tells them: “I think I know what this is about.”

He takes them to the gun, stored neatly in a case, and explains it’s not a real firearm. The two ASU members, both of sergeant rank, are inclined to agree after examining the item. However, they take his details and take away the “gun” for ballistic testing.

On the same night, the Dublin ASU responds to an alert about young men spotted with knives around O’Connell Bridge in the city centre. “There’s sometimes organised fights between these groups – it may have been that,” says one of the ASU members. By the time the unit arrives at the scene, the youths have dispersed.

Dublin ASU members practise a door breaching during their shift.