Murray, you may need a longer chain (I have a 1.5m Oxford one) but you should if you park the bike directly over anchor be able to feed it through the triangle in the frame and out the otherside of the bike, bring the other end of the chain up from under the bike to meet it and then padlock it, it means they would have to cut the frame in two places and dismantle the bike or cut the chain/break the lock.

The other choice you have is to feed it through the the frame on just one side and then lock it, I used this method when I only had a short lock and Webbys 749 in my garage ....