The future would thank us if we had the balls to build real border defenses now.
We've got one, the English Channel. While I was OK with Blair back in the day, I wasn't a fan of the idea of introducing ID cards - thought it was too illiberal. I'm actually warming to the idea now, we probably should take the opportunity on Independence Day next year to look at introducing some form of ID card(s) for both citizens and people who are legally entitled to be here to be used for anything from renting accommodation, gaining employment or making use of government funded services etc...
Would be helpful if the Schengen zone ceased to exist tbh... and frankly it is quite possible that it could fail if a deal isn't struck within the EU re: how to deal with migrants.