Bi-Annual Drill?

This from the UK. Most odd. If this is a bi-annual thing, it's the first time the main stream media have made big deal out of it. Showing large numbers of troops, weapons, vehicles, helicopters etc. Salisbury, UK has been in the news a lot recently. What with Russians being poisoned there, etc. This press report is sending a message to someone (s) and is not just for the British people's edification.