Define very good. If good enough for the "Locks that work" thread then you are doing the best you can to prevent it going, and bikes of similar worth are left poorly locked all around london, so in that respect a thief would be unlikely to go after yours. However no d-lock/chain defeats power tools so if someone specifically wanted it, they could get it in a few unmolested minutes overnight. It's your call if that's a risk you can take...
Define very good. If good enough for the "Locks that work" thread then you are doing the best you can to prevent it going, and bikes of similar worth are left poorly locked all around london, so in that respect a thief would be unlikely to go after yours. However no d-lock/chain defeats power tools so if someone specifically wanted it, they could get it in a few unmolested minutes overnight. It's your call if that's a risk you can take...