In January 2017, in a televised Speaker's House lecture, Lewis stated his belief in the unpredictability of future conflicts; the value of nuclear deterrence; and the role of containment in long-term ideological struggles. He called for three per cent of GDP to be spent on Defence, and for a Statute of Limitations to be enacted "covering everything that took place before the Belfast Agreement", in order to protect Service veterans from legal harassment. Lewis also criticised media suggestions that the next NATO Secretary-General should be David Cameron, given his unsatisfactory record of "toppling Arab dictators in places like Libya, increasing military commitments whilst cutting the Armed Forces, predicting a Third World War in consequence of Brexit, dangerously delaying the renewal of Trident for the sake of Coalition politics".