Short answers, pulled from the story.
Sir Frederick Leith-Ross began urging senior British government figures to revive the World War I blockade strategy in 1937. He had represented British interests abroad for years, including missions to Italy, Germany, China and Russia.
On the 24th of August 1939 a week before the invasion of Poland which started the war Germany announced rationing of food coal textiles and soap. This announcement came even though shortages existed before the war began.
In the first four weeks of the war official figures stated that the Royal Navy confiscated 289,000 tons of contraband. The French Marine Nationale confiscated 100,000 tons during the same period.
Scapa Flow was selected as main British naval base because of its great distance from German airfields. A U Boat crept into the Flow during night of the 14th of October and sank veteran battleship HMS Royal Oak with over 800 fatalities.
Sweden provided Germany with 9 million tons of high grade ore per year via Baltic ports without which German armaments manufacture would be paralyzed. These ports froze in winter but an alternative route ran through Norwegian port of Narvik.