World's largest iceberg twice the size of Greater London embarks on its final journey

Earth's colossal ice giant, A23a, is making waves - quite literally - on what could be its last journey. 

The frozen behemoth, twice the size of Greater London, has broken free after three decades and embarked on a slow, majestic drift northward through the Antarctic seas.

A tooth-shaped iceberg, nearly 4,000 square kilometers in size, reveals itself through the Antarctic mist and fog. 

Expedition leader Ian Strachan recalls the awe-inspiring moment when the clouds lifted, unveiling an expansive white line stretching across the horizon. 

"Then the clouds lifted and we could see this expansive -- almost abstract -- white line that extended each way across the horizon," he said. "All the cracks and arches were different notes as the song played."

This natural marvel, adorned with gaping crevasses and beautiful blue arches, leaves witnesses spellbound.

But the story doesn't stop at the sheer size and beauty. A23a, also known as the world's oldest iceberg, started its journey back in 1986. After being stuck to the Antarctic ocean floor for three decades, it broke free last year. Now, with an estimated one trillion tonnes of fresh water on board, this frozen giant is drifting between Elephant Island and the South Orkney islands.

Experts emphasise the slow, lumbering pace of this iceberg, a 'lumbering beast' that would have been visible to the Titanic on its ill-fated journey. 

The iceberg, currently navigating through what scientists call "iceberg alley," faces warmer waters and bigger waves that could gradually break it apart.

As it follows the path of its predecessors, A68 and A76, there's a slight concern about its proximity to South Georgia island. The fear is that it might block access to feeding grounds for penguins and seals. However, experts believe it's more likely to continue northwards, eventually meeting the fate of all icebergs - melting away in warmer waters.