Line a baking tray with greaseproof paper and set aside.
Cook the potatoes in salted water until tender, about 10-12 minutes.
Drain and steam dry for a few minutes, then mash well and set aside to cool a little.
In a large saucepan, cover the fish in in cold water and the lemon juice.
Bring to a simmer and cook (poach) for 5 minutes until just cooked through.
Remove from the water, remove any skin and flake into large chunks.
Put the lemon zest, herbs, spring onions, tartar sauce and some salt and pepper into a large bowl with the fish and the potatoes.
Combine all the ingredients, then divide into 12 portions and shape into cakes.
Using 3 plates, put the eggs in one, flour and breadcrumbs in the others.
Dip each of the fish cakes in flour, pat off any excess, then dredge through the egg.
Finally, coat in the breadcrumbs and transfer to the prepared baking tray. Repeat with the remaining fish cakes.
Heat the grill to medium. Brush the fish cakes with the oil and grill for 4-5 minutes each side until golden and hot through.
Serve with extra tartar sauce and salad or green vegetable of choice.