The sharp decline in the dollar has prompted sterling to break the $1.80 level today.
The dollar has continued to ease against major currencies, with concerns about the US current account and budget deficits.
This is a new 11-year high for the pound, which last saw such heights in 1992, the year that the UK dropped out of the European exchange rate mechanism.
The euro also hit a new all-time high in London this morning, trading at $1.2687. It had reached a fresh high overnight in Asia, as investors returned from the New Year holiday break.