Investors endured a miserable start to the week after the FTSE 100 Index tumbled 1% on the back of worries over the weak US dollar today.

The firm that provides security for the Tower of London today said it was confident of hitting its annual targets after half-year profits rose 7.8%.

The FTSE 100 Index has made a negative start to the week, falling 13.6 points to 4353.4 in the first hour of business.