It is an aircraft for a subsidiary of British Airways. The airline operates short haul flights in the UK and European destinations. I would assume it is a new aircraft on its way from Brazil where it is manufactured to London. It has a flying range of over 2000 miles, so with a series of stops say in SXM, US, Canada, Iceland etc. it can make it to London. Many smaller aircraft with even shorter flying ranges use the same method to get aircraft made in North America to Europe.