Minder - why is "Slaughter" slang for Arthur's "lockup"?

More questions about slang from the TV series Minder. Why is Arthur's lockup referred to as a "slaughter"?

Slaughter: according to Eric Partridge, a slaughter is "the quiet secluded spot, generally a farm or walled car park, where theives transfer stolen goods from one vehicle to another, split consignments into easier-handled amounts, display items to receivers, and go about their unlawful occasions."

The phrase may be related to "slaughter-house", slang for somewhere a crime a has been committed. And it may also be related to "make a killing", meaning make a big profit.

Since Arthur's lock-up is usually full of knocked-off goods to sell onto shady characters this definition would fit.