As has been said, for the majority of users who are eGate eligible there will be little difference as long as they are staffed correctly. They backfill from other departments - similar to when BA cabin crew used to strike - to ensure the eGates are staffed. At T5 this is likely to be most arrivals.

The army were used a while ago but unlikely to be used again as whilst popular with the public they were somewhat lax in their scrutiny which caused some issues.

One of the problems with a Border Force strike is that for a strike to be effective it needs to impact a significant portion of the public so the Govt will sit up and take notice. But when that portion can access the eGates which, as we’ve seen, will be fully staffed, then any delay or disruption will be minimal. The only delays will be to those who can’t use the eGates, most of whom won’t be U.K. based and so don’t really have a great deal of sway.