Put the cod fillets in the marinade and turn over so they are evenly coated.

Cover with cling film and chill for 1 hr.

2)Put the radishes in a small bowl with the black sesame seeds, the remaining vinegar and sugar, and a pinch of salt.

Leave to pickle for at least 30 mins.

3)For the wasabi tartare sauce, combine all the ingredients and season well.

Set aside or chill in the fridge until needed.

4)Meanwhile, put the sweet potato chips in a large saucepan filled with cold salted water.

Bring to the boil and cook for 7-8 mins until slightly tender.

Drain and leave to steam-dry for 2 mins.

5)Fill a large saucepan with the oil until two-thirds full.

Place over a medium-high heat until the oil reaches 180C on a temperature probe (or until a piece of bread crisps up in 20 secs).

Meanwhile, make the tempura batter by combining the flours and gradually whisking in the soda water.

Whisk until the batter is lump-free, then chill until needed.