Portugal has historical ties with São Tomé and Príncipe, from the period of colonization by the Portuguese. Portugal is the largest investor in São Tomé and Príncipe, investing millions of euros in the economy of São Tomé and Príncipe. São Tomé and Príncipe maintains an embassy in Lisbon, a consulate in Porto and one in Coimbra. Portugal maintains an embassy in São Tomé. Portugal and São Tomé and Príncipe signed an agreement, in which Portugal undertakes to patrol the coastal area of São Tomé and Príncipe, protecting it mainly from pirates. The Portuguese military ship NRP Zaire and some Portuguese patrol boats are permanently stationed on the coast of São Tomé and Príncipe. The economy of São Tomé and Príncipe is closely linked to that of Portugal, with Portugal accounting for more than 50% of imports from São Tomé and Príncipe. Portugal has also helped to develop education in São Tomé and Príncipe, financially helping to build and maintain the Public University of São Tomé and Príncipe. The Portuguese President Marcelo Rebelo de Sousa visited Sao Tome and Principe in 2018 to demonstrate the strong economic and cultural ties between Portugal and São Tome and Principe.