Preheat the oven to 180°C, fan 160°C, gas 4. Stuff the chicken cavity with one of the lemons and half of the thyme. Put the chicken into a large roasting tin, breast-side up.
Mix together the chilli paste and red pepper purée and spread over the chicken with a butter knife. Roast on the middle shelf in the oven for 1 hour 10 minutes.
Add the remaining lemon and the potatoes to the roasting tin 30 minutes before the end of cooking time. At the same time, top the Mediterranean veg with the remaining thyme and put the trays in the oven to cook.
At the end of the cooking time, check the chicken is cooked – the juices should run clear when you pierce the meat with a skewer. Remove the chicken from the roasting tin and rest for 15 minutes before carving, and serving with the roasted vegetables.