In 2015 assets that the UK holds abroad fell in value relative to the stock of assets held by foreign investors in the UK

UK Balance of Payments, The Pink Book 2016 Main Points:

In 2015, the UK recorded the largest current account deficit as a percentage of GDP among the G7 economies.

The deterioration in the current account balance in recent years, leading to a record deficit of 5.4% as a percentage of nominal GDP in 2015, was largely due to UK earnings on assets overseas falling relative to the earnings of foreign investors in the UK. The decline in the primary income balance in recent years has been due to both; the stock of assets that the UK holds abroad falling relative to the stock of assets held by foreign investors in the UK; and the rate of return the UK receives on its assets abroad slightly falling while the rate of return earned by foreign investors in the UK slightly rising.