Perhaps this is where the 300,000 estimate comes from. (see below)First thing you need to understand is method of entry and that people are counted in and counted out. So right away there are illegal migrants we know about.
https://www.migrationwatchuk.org/key-topics/illegal-immigration
These are the over-stayers. The ones who cannot work, cannot claim benefits and must rely on family and friends.
://www.migrationwatchuk.org/briefing-paper/190
But some attempts have been made to estimate the total size of this population putting the figure anywhere between 300,000 and more than a million.
https://www.bbc.com/news/uk-43837834
A long way off the estimate 1.1 million.https://www.bbc.com/news/uk-43837834
Migration watch, of course being a right wing organisation wanting to reduce immigration.
So according to you, our border force is a waste of space?
It's going to get even more difficult post Brexit when we have to monitor EU citizens in and out.
There will be far more illegal migrants to catch, process, and deport etc.