Dual National rights and Indefinite Leave to Remain UK

[ZIM01]

Require advice on Dual National rights; I got 2 citizenship UK and another foreign country, on my old foreign country passport I got Indefinite Leave to Remain UK since 1993. Each time I travel to overseas to my country of origin I use my foreign country passport which got Indefinite Leave to Remain UK since 1993. I Use this other passport to leave UK and enter my country of origin, and on my return to UK I have to use my foreign country passport which is got my Indefinite Leave to Remain in UK, When I enter UK I get lot of hassle from Immigration agency at LHR they want me to use my British passport to enter UK. This is a rule or just command from individual immigration officer? I had call one of Immigration solicitors and they have advise me, even there I got dual citizenship UK passport I can still use my other foreign passport to enter UK without no obligation as my Indefinite Leave to Remain UK is from 1993 ? Any one can advice on this topic please.

[vinny]

Indefinite leave isn't applicable to British citizens.

You should leave/enter the UK with your British passport.
Enter/leave your country of origin with your foreign passport respectively.

[secret.simon]

I got 2 citizenship UK and another foreign country

Is the second country India (based on the flag on your profile)? If so, and you acquired your British nationality by naturalisation or registration (rather than by birth), then you will have lost your Indian nationality/citizenship automatically on acquisition of British nationality.

British citizens cannot have ILR and therefore your ILR ceased when you became a British citizen. That is why the Border Force/immigration officials "hassle" you when entering the UK. Your ILR is no longer valid and you need proof of your British citizenship (either a British passport or a CoE-RoA in a foreign passport) to enter the UK without hassle.