Hi,
Your government pension is not taxable in the UK and does not need to be reported to HMRC.
Article 18, relates to government pensions derived from government employment in Hong Kong, for services rendered in Hong Kong.
Where this criteria is met, the pension is only taxable in Hong Kong.
Article 10(1) of the double taxation agreement (DTA) advises that dividends paid by a Hong Kong resident company to an individual resisdent in the UK, is only taxable in the UK.
Article 11 of the DTA advises the interest of an individual arising in HK and paid to a UK resident is taxable only in the UK
UK/HONG KONG DOUBLE TAXATION AGREEMENT AND PROTOCOL
The fact that you have foreign income that is taxable in the UK, is self assessment criteria, regardless of the amount, so you will need to complete a tax return.
Check if you need to send a Self Assessment tax return
Thank you.