By Jack Barnett City traders today were boosted by signs of inflation cooling in the world’s biggest economy sparking a rally on Wall Street. London’s premier FTSE 100 index climbed 0.25 per cent to 7,507.11 points, while the domestically-focused mid-cap FTSE 250 index, which is more aligned with the health of the UK economy, surged nearly two per cent to close over the 20,000 mark. Investors were seemingly exercising caution during the morning session before new US inflation figures were published in the afternoon. The rate of price rises across the pond cooled to 8.5 per cent, much lower tha…