Sonne
... that the German Sonne radio navigation system proved so useful to the British during WWII that they provided spare parts to keep them running?
... that the German <b id="mwBBM"><a href="./Sonne_(navigation)" id="mwBBQ" rel="mw:WikiLink" title="Sonne (navigation)">Sonne</a></b> <a href="./Radio_navigation" id="mwBBU" rel="mw:WikiLink" title="Radio navigation">radio navigation</a> system proved so useful to the British during <a href="./World_War_II" id="mwBBY" rel="mw:WikiLink" title="World War II">WWII</a> that they provided spare parts to keep them running?