GRS officers start foot patrols in the early evenings. | Alejandro Sepúlveda

The GRS, Reserve and Security Group, is an elite Guardia Civil unit which is deployed in Mallorca on occasion for the likes of major drugs busts. The unit's principal function is public order in situations that are considered to be "sensitive".

Some thirty GRS officers have been sent from Valencia to Calvia. Over the summer, they will operate in the municipality's main resorts - Paguera, Palmanova, Santa Ponsa and Magalluf. They are based in Magalluf, their operational centre being the SATE foreign assistance service office.

The GRS is a formidable unit. Officers are armed with Sig Sauer 553 assault rifles and Heckler & Koch USP Compact semi-automatic pistols. They are equipped with tablets that include the SIGO Integral Operational Management System, a rapid database for tracking identities and number plates. Driving powerful Toyota SUVs, they set up lightning road controls with chains and spikes. These controls last no longer than ten minutes. They keep moving because of alerts to drivers via messaging systems.

During the day, some officers are stationed on the roofs of frontline hotels. They scan the beach with binoculars. In the evenings and at night, they are on patrol - by foot and in car. They are not to be messed with.