Request for Certificate of Residence in the UK - Article of double taxation agreement

I am a Spanish citizen living in the UK since 2014, I have inherited a 25% of a pension fund my father had in Spain before passing away a few months ago. The company holding the funds are asking me to present a certificate of tax residence in order to release the money. I've read the double taxation agreement between UK and Spain but I am unsure which article applies to my case. To give more context, in Spain these funds would be treated as income, not as an inheritance, hence why I think maybe articles 20 and 22 apply to this situation. If you could provide any guidance that would be much appreciated. Kind regards,

Hi whats next,
It is Article 4 as it is based on residence.
Thank you. 

Hi, I am in a very similar situation to whats next. I just got the CoR but I'm unsure of how this money will be taxed. I understand that it should not be taxed at all in Spain and it should be taxed as Foreing Income in the UK through Self Assessment (being taxed in the resulting band when added to income in UK). Is that correct? Thanks in advance

Hi,
A certificte of residence is issued where the UK has a tax treaty with a foreign country (in this case, Spain) and the individual has income arising in that foreign country.  
The certificate is used to support the individual's claim to repayment of any tax on that income, deducted in the foreign country.  
It is your supporting evidence, to show that you are tax resident in the UK and only taxable on this income in the UK.  
You then declare the foreign income in your self assessment tax return.
Thankyou.