This is what losing looks like.

The British are seeking to establish tripwires in western Ukraine and the Black Sea.

Best case scenario:

The British foresee that this war is going to drag on for years to come and they are seeking to expedite the training of new recruits while reducing the cost.

Mediocre scenario:

The British foresee the risk of Ukraine losing ground and they are seeking to establish redlines in Western Ukraine to prevent Russia from taking the entire country.

Worst case scenario:

The British are seeking to station forces on Ukrainian soil and in the Black Sea to use as a pretext for declaring war on Russia in the case that a British serviceperson or vessel inevitably cops a wayward Russian projectile.