Quote from an 'MoD source': "we don't want to resort to deploying the armed forces to deal with political failings".
Historically, isn't this what armed forces have been used for..?a https://www.thetimes.co.uk/article/migrant-boats-to-be-pushed-back-before-they-reach-british-waters-v69c9dk9f

And another issue: if the government of the day deems this a suitable requirement, should not CDS AND FSL, after suitable briefing and caveats, snap a sharp salute, turn to the right, and march off to implement policy?

Here's an unfashionable thought: the RN's 2 most important tasks for the next 12-18mths (unless WWIII breaks out, for sure) are now migration patrols and fisheries protection. Both have resonance with the public, let alone the government.

Basically, with a defence review and a spending review on the horizon, now is not a really good time to be briefing against the government. Fairly well-known that the PM is highly vindictive, Cummings as well/more so.

By all means tell them that you require orders/reqts in writing, but I fear that there will be only one winner in any "back briefing battle".

For both fisheries protection and migration patrols, if called upon to do these, they become reputational issues for the RN/MoD - shirking will not be viewed well...