Several months after a string of tit-for-tat tanker arrests in Greece and Iran, diplomatic talks to secure the mutually agreed release of three vessels blocked in the two countries have failed to make any visible progress.

The 157,400-dwt Delta Poseidon (built 2011) and the 150,000-dwt Prudent Warrior (built 2017), two Greek-flagged suezmaxes with about 50 seafarers on board, have been held by Iran since 28 May as a bargaining chip to free the 115,400-dwt Lana (built 2003) — an Iranian-flagged aframax immobilised in the Aegean Sea since mid-April.