In a medium bowl, pour in 120ml olive oil.
Add 60ml soya sauce and 30ml Worcestershire sauce, then stir to combine.
Stir in 15ml packed soft brown sugar until it starts to dissolve.
Add 2 garlic cloves, minced, 1 tsp dried thyme and ½ tsp freshly ground black pepper, then whisk until the sugar is completely dissolved.
Place 800g steak in a shallow dish or a resealable bag and pour over the marinade, ensuring the meat is fully coated; seal or cover.
Chill in the fridge: marinate thinner cuts for 30 minutes to 2 hours, or thicker cuts for 4–8 hours.
When you're ready to cook, remove the steak from the marinade and pat dry with kitchen paper; discard any leftover marinade.
Preheat a barbecue, switch your oven to grill, or heat a cast-iron frying pan until very hot.
Cook the steak to your liking (for medium-rare, aim for an internal temperature of 54–57°C).
Rest the steak for 5–10 minutes, then slice against the grain and serve.