mycar was stolen in a trade

I was trading my jaguar for an aston Martin vanquish he sent me the pics I trusted him like a dumbo and delivered my car to a airport parking where I met him he. Came with his freind his freind sat in my car I had the keys for the Aston the moment I got the keys His other freind came from the back and took the keys ran and left in both the cars now I found my car outside a bar in London and the metropolitan police won't except the car was mine until I showed the docs and they would not let me take the docs from the car so. Now because of that I've lost my car and come back to India a d lost it all....