Visitors, many from around the world, waiting to visit the Acropolis archaeological site on Tuesday morning were in store for an unpleasant surprise, as a union representing guards declared what it called a 24-hour “warning strike”.

According to the union (PEYFA), which represents guards at archaeological sites around the country – all of whom enjoy civil servant status – the industrial action was declared in opposition to a tender for ticket-issuing, entry and validating machines at the Acropolis.

Although an Athens first instance court ruled the strike as illegal, the union used a “loophole” entailed in declaring consecutive four-hour work stoppages.

Long lines of visitors waiting to enter the Acropolis site have long plagued the country’s tourism image, with the current culture ministry leadership has promised to use digital tools and online ticket sales to cut wait times.