Billboard hacking started when commercial messages appeared in public space. In the first centuries BC, inscriptions promoting gladiatorial battles on the houses of the wealthiest in Pompeii commonly encountered passers-by who would inscribe their own humorous or insulting responses. The commercialisation of paint markers and spray paint in the 1960s helped popularise the practice. During May 1968 protests in Paris, protesters wrote over billboards to give voice to their messages.