This island built by nature for herself against infection

The following is quoted from Adrian Hilton's book The Principality and Power of Europe. 

These are the words with which the book concludes.

The shift towards European Government has gone so far that failure to insist upon renegotiation or preparation to withdraw undermines the very principles that the Conservative Party exists to promote — the national interest and the self-governance of the British people. Just as Churchill called the nation to prayer on the eve of the Battle of Britain, the current threat from the Continent is no less worthy of constant prayer, and the call is just as urgent. It is a righteous government which will restore British sovereignty, pursue righteous laws and maintain the Constitution of liberty which has served Britain for centuries and by which the Gospel has been freely proclaimed. Britain can be restored to her sovereign greatness, and the Word of God clearly states that 'Righteousness exalteth a nation' (Proverbs 13:34). 

Britain has developed a remarkable political system and an enviable Constitution, and has the unique record of not being invaded by a foreign power for 1000 years. Its tried, tested and trusted institutions have provided stable and responsible government for centuries, reinforcing the view of this 'island built by nature for herself against infection and the hand of war.' Having many times been victorious against the overt hand of war, it is surely now time to guard against the subtleties of infection.