Wasabi, or Japanese green horseradish, is also known among sushi connoisseurs as namida, meaning tears. This hints at what can happen from misguided use, but you don’t have to be a connoisseur to experience the delights and agonies of this unique ingredient, as my English husband and I once witnessed in a Japanese restaurant near Covent Garden. A broad-faced Scot walked in armed with a London guidebook and expressed his desire to sample a typical Japanese meal, apparently for the first time. A commendably brave man, I thought to myself. Two Japanese waitresses dressed in kimonos flitted around, escorted him to the counter a few stools away from us and assisted him with the menu. My husband and I observed a short exchange of high-pitched giggles and throaty grunts while we got on with our lunch. A plate of sashimi (slices of raw fish) was soon presented to the awaiting Braveheart. He surveyed the plate briefly, nodded, adjusted himself in the seat and began to work his way diligently from the left to right of the plate. I watched his amateurish but determined efforts with chopsticks with curiosity and a certain admiration. He was evidently enjoying every mouthful as he sampled each slice of fish, especially the salmon. But then I grew increasingly alarmed: he was heading intrepidly towards a piece of green wasabi paste, beautifully shaped into a leaf, on the right-hand corner of the plate. I elbowed my husband and whispered: “For goodness sake tell him not to eat the wasabi leaf!” A sly grin appeared on the Englishman’s face. “Why spoil the fun of watching a Scotsman cry?” he replied, as the unsuspecting tourist dissolved into tears of scarlet-faced distress.

Wasabi, which is gaining a new-found popularity in innovative western cuisine, is a perennial aquatic plant that grows wild across the temperate regions of Asia. In Japan it is cultivated in remote mountainous areas, growing in crystal-clear waters at a steady 12-13ºC with the plants protected from direct sunlight. It grows to 30-40cm tall and has attractive glossy green heart-shaped leaves with jagged edges. Although the whole plant has a pungent tear-jerking smell, it is the root that is used in Japanese cuisine.