7 attack subs
Yow. If this happens, Britain will have fewer warships than the Imperial Japanese Navy lost in just one battle, Leyte Gulf. (Where, for the record, the U.S. Navy sent to the bottom 4 carriers, 3 battleships, 8 cruisers and 12 destroyers.) Or less than half the 63 galleons and armed merchant vessels the Spanish Armada lost, mainly to storms.
Thomas E. Ricks covered the U.S. military for the Washington Post from 2000 through 2008.