Hi,
The double taxation agreement between the UK and Hong Kong, advises that pensions and other similar remunerations, arising in Hong Kong and paid to a resident of the UK, are taxable only in Hong Kong.
For this reason, it should not be included in your self assessment tax return. Article 17 of the DTA Agreement between Hong Kong and the UK applies:
UK/HONG KONG DOUBLE TAXATION AGREEMENT AND PROTOCOL
Please also see the following Guidance:
DT9203
Thank you.