Long Term Residents tax

From what I see direct taxation in The Gambia is horrific - 35% on all income. I also see The Gambia operates a double taxation agreement with the UK. Does that mean one is automatically excused tax on income from overseas in The Gambia if one is already paying tax in the UK or is there something one must do in The Gambia to avoid being caught?

dont take out gambian resedencey and dont stay in gambia for more than 183 days(i think thats the correct no but check)or you will be classed as a resedent