Cook potatoes in boiling water. Drain and mash; transfer to a large bowl with sweet chilli sauce, fish sauce, tuna, zest, coriander, breadcrumbs, celery and egg. Mix well.
Divide mixture into four and shape into patties.
Preheat a barbecue or frying pan on medium high. Add oil and fish cakes, cook 5 minutes each side or until golden.
If desired serve with extra sweet chilli sauce (optional) and lemon wedges.
