In a large frying pan, cook bacon until crispy; transfer bacon into a roasting pan but keep bacon grease in pan for browning the roast.
Rub beef with salt and pepper; cook in the bacon fat until just browned on all sides, about 5 to 7 minutes.
Add onion, garlic and carrots to the roasting pan. Set roast on top. Pour in 200ml beer, hot beef stock and fresh thyme; cover with foil.
Roast in preheated oven for 90 minutes.
Remove the roast beef from the roasting tray and set aside to rest. Transfer the vegetables to a serving plate and keep warm. Pour the meat juices through a sieve into a small saucepan; bring to the boil and simmer for a few minutes.
Melt butter in a small pan and stir in flour. Ladle some of meat juices into the flour mixture, whisk until smooth. Add to the saucepan with meat juices; stir well and cook over low heat until thickened into a gravy.
Slice the roast beef and serve with warm roasted vegetables and gravy.