Place your whole chicken in a large pot and cover with water until it is submerged by about 5cm. Bring to the boil, skimming the froth off the surface when necessary. Simmer for 30 minutes.
Add the chopped vegetables, garlic, peppercorns and bay leaves, and season with a good pinch of sea salt. Bring back to the boil, then turn the heat down and leave it to simmer for 1 hour. Keep an eye on the broth, skimming when necessary.
When the soup has been cooking for an hour since adding the vegetables, use tongs to carefully transfer the chicken to a roasting pan with deep sides. Leave to cool, uncovered, for a few minutes. Remove the soup from the heat and strain it through your biggest sieve or colander into a large bowl or pot. Return the strained soup to the heat and bring back up to a simmer.
When your chicken has cooled enough to handle, either use two forks or use your hands to shred the meat off the bone. Pile it on to a plate and add the skin and bones back to the pot to simmer for 20 minutes. Strain again before placing back on the heat and adding your orzo. Bring back up to the boil for 15 minutes or until the orzo is almost cooked. Add all your shredded chicken meat to the soup and warm through for 3 minutes. Have a taste, and season with salt and pepper.