FTSE 100 today slips as pound jumps and gold hits $5,300; Marston’s dives

The FTSE 100 is the flagship stock index of the London Stock Exchange, tracking the 100 largest companies by market capitalization listed in the UK. Often called the “Footsie,” it serves as a barometer of British large-cap equities. The index is market-cap weighted, meaning each company’s influence on the index is proportional to its market valuetheguardian.com. In practical terms, bigger companies like Shell or HSBC move the FTSE 100 far more than smaller constituents. The FTSE 100 is maintained by FTSE Russell and is updated in real time during trading hours. It’s also a basis for countless investment products – from index funds and ETFs to futures contracts – giving investors a way to track or trade the overall London market easily.