The security bill for the visit of Prince William and Kate Middleton this week will cost upwards of €1m, the Herald understands.
As third in line to the British throne, William and his wife will have high-level security operations in place for their visit from tomorrow until Thursday.
Temporary road closures will be in place to ensure smooth travel for the couple and the Emergency Response Unit (ERU) will be responsible for moving the couple around, although it is expected they will bring their own armoured vehicle.
As part of security measures before their arrival at some locations, drains will be welded shut on public streets to ensure explosives cannot be planted in them, sources have told the Herald.
For all public walkabouts, garda sniper teams will be deployed on rooftops.
The proposed walkabout in Galway, which will involve meeting local business owners and community leaders, is expected to be the biggest logistical nightmare.
Gardai have notified traders that road closures will be in place from 6am to 2pm in Williamsgate Street, Williams Street, Shop Street, High Street, Mainguard Street and Abbeygate Street. Vehicles have been banned from parking in the surrounding area to prevent any potential threats.
Royal protection officers from the Metropolitan Police will accompany the couple, working in tandem with a team of 12 members of the elite ERU, who will oversee their day-to-day security and are trained in close protection and overseeing security for VIPs.
As the official Irish State guest house, it is believed Kate and William will be staying at Farmleigh House for their two nights' stay, following in the footsteps of William's grandmother Queen Elizabeth and his brother and sister-in-law Prince Harry and Meghan Markle, as well as Canadian Prime Minister Justin Trudeau and the Emperor and Empress of Japan.
The queen's security cost an estimated €20m in 2011 in what was considered an unprecedented amount given the level of risk and attention involved, amplified by the fact she and Prince Philip stayed for three days.
Harry and Meghan's security cost the Irish taxpayer €300,000 over the course of 36 hours, and Prince Charles's May 2017 visit cost just over €2m.
During Charles's visits over the years, gardai have carried out security sweeps of nearby areas and notified relevant members of the public.
While much of Kate and William's itinerary is embargoed and the logistics are being kept secret to ensure their safety, all journalists applying to cover their visit have been vetted by gardai.