Why does Iceland want Scotland's fish?

There seems little end in sight for the international dispute on the rights to fish Scotland's most valuable stock, a bitter row that is entering its fifth year.

Iceland has just set another year's quota for mackerel. A move which defies scientific guidelines on sustainable fishing.

The Scottish industry says the stock will soon be ruined.

Why such defiance? BBC Scotland's Kevin Keane has been to Iceland to find out.