Securing a Brooks saddle against theft

I live in London's famous London, bike theft capital of wherever.
I want to use a Brooks, but also lock my bike up outside often.
How can I secure it to the frame? The options seem to be:

• Use a hexlock/ball bearing glued into the seat post pin/saddle clamp bolt. Does this work?
  
• Take an old chain and loop it through saddle rails and top tube. But I've heard of others having this chain cut and then they take the saddle straight away.
  
• Take the seatpost and saddle off every time you lock the bike. Can't be bothered with this.
  
• ??
  
  

Any comments welcome.