Love can trigger a search for a new place to live - and what you learn about property can grow into an interesting sideline.

In an increasingly litigious world, accidents trigger a search for blame, and aspersions of blame often trigger ensuing litigation.

This triggered a search in an area of about 600 square miles, deploying a submarine that can dive to 6,000 metres.

This triggered a search for a suitable heir.

All of these triggered the search for a more capable system.