How long does a 0.7KG Leg of lamb take to defrost?

Leg of lamb shouldn't have been frozen in the first place. If you are going to make leg of lamb, make it fresh. But, no, it MUST be defrosted before you cook it. Otherwise, the inside will never cook to temperate and you will risk food poisoning. Also, I hope you did not leave it sit out for 6-7 hours defrosting as that is something you should never do. Always defrost in the refrigerator, or if you must, a microwave but never let meat sit out or sit in sink of water to defrost.