I have a 1.2kg whole chicken that I wish to roast, on the packet it says it'll take 1h 28m at 200°C.
The New Best Recipe book recommends cooking a 1.8kg chicken for just 60m, with temperature of 190°C for 30m and 230°C for about 30 more. Nigel Slator's Real Cooking recommends a similar 60m time for a 2kg bird, with a variation on the cooking temperatures. And Delia says to cook a 1.6kg chicken for around 60m too.
Why are the times so radically different? Accounting for the weight, it would seem that the packaging recommends almost twice the cooking time that the reliable professionals recommend. Is the shop just being overly safe?