Here are three issues your security consultant should address:

1. The physical layout of your property and how to protect it. Police often recommend that large country estates install perimeter fencing, hidden barricades known as Ha-Ha walls, driveway bollards and closed-circuit television cameras with video recorders.

2. The alarm system and hidden security devices—from trackers to digital motion detectors to DNA markers. (A DNA marker is a varnish-like liquid that can be painted into the nooks and crannies of an artwork or on the back of a canvas. The marking liquid contains a chemical code unique to that sample that is recorded on a computer database. The police, using ultraviolet scanners to identify the varnish, can easily track the art back to its original owner once it’s been recovered.) Do they suit your collection, your lifestyle and travel schedule?

3. Control of who is coming and going and who has access to the collection. This could mean anything from running a background check on the maid to vetting the construction crew remodeling your kitchen. “Nowhere is 100 percent secure, but by creating rings of security, you create an effective deterrent,” says Geddes. “For the thief, the risk becomes too great.”