The savoury spread, which people are said to either love or hate, is made with yeast from four specially-selected breweries.

Marmite Extra Old, or XO, which will hit supermarket shelves from March 8, is the result of the secret blend maturing for 28 days - four times longer than the standard product.

This allows the flavour and texture to intensify, creating a spread so strong and full-bodied it can only be appreciated by the most devoted fans, according to the manufacturer.

The XO recipe was developed with the help of the "Marmararti" - a group of committed and vocal Marmite fanatics who tried samples and gave feedback on the flavour.

Marmite developer Grahame Walker said: "XO was created purely for passionate lovers to indulge.

"Whilst the overall characteristics are the same as the original recipe, the specifically developed formulation and longer maturation period allows the flavour and thicker texture to develop to a much higher level.

"The resultant blend creates an intense sensory experience that can only be appreciated by the most extreme Marmite devotees."

Marmite XO has a recommended retail price of £3.99 and comes in a black and gold jar housed in a black presentation box.