International cooperation is important, but over reliance on a single foreign partner, even a close ally causes risks. It leads to a situation where a country possesses shiny new military hardware but lacks the logistical support, sovereign weapons integration, skilled personnel, and overall control to use it effectively and autonomously.

I imagine the UK's experience with the F35 is a major driver in it's decision to partner with Japan and Italy on the next gen Tempest fighter, so they can regain sovereign control over its future air combat capabilities.

However, the problem extends beyond the F35. Although the UK has increased its defence budget in real terms, the extra funding has been outstripped by soaring equipment costs (Boeing mark up the costs of soap dispensers by 7,943%!), the legacy of decades of under investment, and the spiralling expense of strategic programmes like the nuclear deterrent. The budget for conventional forces does just not exist.