UK stocks opened lower on Monday as uncertainty over U.S. trade tariffs weighed on sentiment, while the pound strengthened against the dollar and broader European markets also retreated on trade concerns. The FTSE 100 fell 0.1% by 0832 GMT, with the British pound gaining 0.24% to reach $1.3518. Germany's DAX dropped 0.4% and France's CAC 40 fell 0.1%, reflecting widespread market unease.

Over the weekend, U.S. President Donald Trump announced a new global tariff under different legal authority, initially set at 10% and later raised to 15%, after the Supreme Court struck down most of his earlier tariffs. The ruling determined that emergency powers used previously did not authorize the tariffs. This policy uncertainty has dampened investor sentiment across European markets, with traders reassessing the potential economic impact of the new trade measures.

Among notable UK companies, Smiths News PLC (LON:SNWS) received a warning notice from the UK's pensions regulator concerning the Tuffnells Parcels Express pension scheme, while Rolls-Royce Holdings PLC (LON:RR) is seeking up to £200 million in government funding for its £3 billion UltraFan aircraft engine development. Johnson Matthey PLC (LON:JMAT) extended its Catalyst Technologies sale deadline to July 21, 2026, reducing the transaction price to £1.325 billion. These corporate developments unfolded against a backdrop of broader market concerns about trade policy and economic growth.