When I lived in London there was a crime wave of bikes being stolen. It took two years to catch the gang.
They used a sound proofed van to render any alarm useless. Two short lengths of steel pole, one through each wheel, 4 guys and the average sports bike was gone literally in seconds. I had an XJR 1300 Yamaha. Being London it had to stay on the street at night. High quality chain and lock around a lampost, plus a vibration sensor alarm kept it safe. They did get my first expensive bike cover. I then looped the chain through the cover as well. The two together are needed. Few other methods will deter the professional bike thief. If the thieves have to fiddle with chains etc. it will set off the alarm so choose an expensive chain and lock. The next best thing, good insurance!