I have a 12 year old labrador who loves being in the house with company. Over the years when we have left him all day alone outside he sometimes dug up the garden.But in the last few months he has dug up all my plants and one day scatched the back door, he got inside and dug up my leather recliner chair. Another day my son left him inside and he dug up his mattress. When we go to our holiday house we leave him inside or outside all day and he won't do a thing. When I am home I leave him outside and only let him in at night, he behaves. He used to sleep outside but now because he seems to be getting old and has trouble with his back legs my husband lets him in to sleep in the warmth. Please can you give me some advise on what I could do to stop this bad behaviour.

In your case I think it will do good if you check your dog for his nails. It many times happens that when the nails increase in size they irritate the dog and then he starts expressing his irritation in the form of such behaviour. Moreover you can also see if he has any wound or sore which is causing him problems. Generally dogs are very sensitive and they like to be around people and do not like to be left alone. But this is only for the early months and they later adapt to the family habits. But later when they become old they again cannot control their anger of being left alone. Just like our older generation cannot control temper and get frustrated in life sometimes.
So I would suggest that you get some fiddle or some new toy for your dog which keeps him occupied. These are also available in the shape of a bone which they keep gnawing to keep them occupied.