london britain nato ally must defend deep sea cable potentially catastrophic attack russia navy could disrupt trillions dollars financial transactions head britain arm force warn cable crisscross world oceans seas carry 95 percent communications 10 trillion daily transactions new risk way life vulnerability cable criss-cross seabeds bbc quote stuart peach chief defense staff say peach say russian president vladimir putin modernization mighty soviet navy pose serious threat western communications russia addition new ship submarine continue perfect unconventional capabilities information warfare peach say russia repeatedly dismiss western concern renew assertiveness cold war hysteria though kremlin supporters praise putin home put restore russia clout 1991 collapse soviet union britain say west must defend undersea cable russian navy