Place the radish in a preserving jar. Place the water, vinegar, sugar, salt, pepper and coriander in a pan, bring to the boil and pour over the radish. Seal the preserving jar immediately, leave to cool, refrigerate for at least 2 hrs.
Radish greens pesto
Puree the reserved radish greens with the garlic and all the other ingredients up to and including the pepper until the pesto is creamy.
Brush the steaks with oil, season.
Charcoal/gas/electric grill: Cover and grill the steaks over/on a medium heat (approx. 200 °C for approx. 3 mins. on each side. Cover and leave to rest for approx. 5 mins. Carve the steaks across the grain, serve with the pickled radish and radish greens pesto.