Roast sirloin of beef & Port gravy

INGREDIENTS

• 3 garlic cloves , finely chopped
• 2 tbsp thyme leaves
• 2 tbsp olive oil
• 1.5-2kg/3lb 5oz-4lb 8oz piece rolled sirloin of beef
• 1 garlic clove
• 1 bay leaf
• few thyme sprigs
• 75ml port
• 350ml red wine
• 200ml beef stock (if you'd rather make your gravy alcohol-free, simply double the quantity of stock)