A gripping, long-running mystery has been unfolding for the past two years, centered around a Greek businessman who claims to be an art dealer and collector.

“We needed to stay up late last night and continue today,” said Greek PM Alexis Tsipras from Sofia, referring to his talks with FYROM Prime Minister Zoran Zaev.

Greece's Prime Minister Alexis Tsipras is due in the Bulgarian capital Sofia on Monday in order to attend the Greek-Bulgarian High-Level Cooperation Council.