@DoctorAllcome, I take back what I said about you being resentful and would like to thank you for guiding me to the articles explaining why the observation may have been made in my son's UK passport.
I have extracted below the relevant articles from the document that you provided the link to where the HMPO have inserted the observation making reference to the details of my son’s country X passport. I have also included my comments where applicable, in parentheses.
Incidentally, my other children have no observations listed in their passports though they were issued under the same personal circumstances (4 names in their birth certificate, 4 names in their country X passport and 3 names in their certificate of registration). Anyway, let’s assume that I requested the HM passport office to drop the grandfather’s name from my son’s UK passport keeping the first name, the father’s name and the surname how is this a name change! And only if you are issued with a UK passport with a ‘so called’ name change are you mentioned as a dual national. Minor changes to forenames or surnames under article 5.2 mentions that when someone is adding a forename, then evidence of change of name is needed. Where an applicant has removed/added a hyphen in cases of double barrelled surname, this can be accepted without documentary evidence providing the spelling and the order of the names remains the same. (So, do I send the HMPO a copy of the same birth certificate that was sent to the home office to apply for the certificate of registration or am I going to be asked that I need to change the certificate of registration?).
6.5 There are individual categories of applicant who may experience restrictions on their ability to meet the identity requirements of one name for all official purposes (if this is the concern of the applicant then the home office should issue the certificate of registration in the applicants legal name namely, the name given in the birth certificate). These are primarily people who have dual nationality and who hold, have held or can obtain in the future a passport issued by another country. In the event that the home office have decided to issue a certificate of registration in a simplified version of his name (3 instead of 4 by removing the grandfather’s name then the home office should issue a letter with the certificate of registration highlighting that the individual mentioned in the certificate of registration is also known by his other name(s) mentioned in the birth certificate and country X passport – not on a UK passport!. And if I need to justify such change I will present the letter to various authorities).
6.6 Subject to the applicant being able to satisfy the following requirements, a passport may be issued in the name requested even where it differs from the name on the passport issued by another country (I have not made such a request – HM passport office issued my son’s UK passport as per the name in the certificate of registration that was issued by the home office! The home office had a copy of my son’s birth certificate (issued with 4 names and a copy of his country X passport issued with the same 4 names). When I requested them to correct it they said that the home office does not re-issue certificates of registration once they are issued and they refused to correct it. Incidentally, my certificate of registration is issued with the same 4 names that are on my birth certificate and country X passport and also on the UK passport. All are issued with the same 4 names. There are no observations in my UK passport and so no reference to me being a dual national. Further, my other children are issued with UK passports with 3 names instead of 4 and no observations are mentioned in their passports).
“The following categories may be given exceptional consideration:
i. The law in the applicant’s country of origin restricts or prevents a change of name. Where there is such a restriction, the applicant will be required to provide evidence from their country of origin that a change of name is not permissible; (I have neither requested nor provided evidence on my passport application). NOT APPLICABLE!
ii. NOT APPLICABLE;
iii. Where there is a requirement for the person to travel to their country of origin in order to change their name (I have not made such request), This may be applicable if I want to now change my original name in my country of origin to a different name shown on the UK passport). Will country X not request a court document authenticated by the UK foreign office and certified by the Embassy of country X to confirm the name change – why mention it in a passport), and due to exceptional circumstances in their country of origin, they would be placed at a high level of risk (what risk?);
iv. NOT APPLICABLE;
6.7 In the case of points (i) and (iii) above, a (British) passport may be issued and an observation placed in the passport saying:
“The holder has a [country] passport, number [ ] issued on [date] in the name of [ ]. This passport is due to expire on [date].” (based on (i) and (iii) above the observation should not have been placed)! Since I have not made such a request.
6.8 Consideration should be given to issuing a restricted validity passport on point (iii).This should be done in conjunction with the Operational Delivery Standards and Guidance Team who will consult with the Foreign and Commonwealth Office. (NOT APPLICABLE).
6.9 In the case of (iii), the requirement to travel to the country of origin in order to change the name of the local passport is a matter for the applicant for a British passport. Country-by-country information on dual nationality is available on GOV.UK, although this is not comprehensive. Applicants should contact their own embassy or high commission or use the website provided by individual countries. (same as 6.6 (i))
6.10 In the case of (iv), the details of any previous passport held should not be disclosed (interesting!!) unless it relates to the same gender as the passport to be issued. The applicant will be required to provide the same level of supporting documentation.
6.13 The British passport will not routinely contain an observation of other passports held by a dual national (So, clearly the object of the HMPO is not to reveal the applicants other nationality(ies)!) unless by exception (see paragraph 6 above) it is in a different name (so a dual national with a name change is at a disadvantage and cause for revealing his other nationality). It is a matter for the passport applicant to raise at the point of application whether providing details of existing or previous overseas passports causes any particular concern (why is this not mentioned in the UK passport application form such that the applicant is aware and able to highlight his concerns before the passport is issued). The home office have no right to issue a certificate of registration that is different from the birth certificate which is the most legal document) or a document issued by the court indicating a legally changed name. The home office should issue a certificate of registration compatible with the birth certificate. If the applicant then decides to drop a name or change a name he will do so in the passport – it is always easier to drop a name than to add a name. In any event, when the name of the applicant is shortened such as in the case of my son then his full name should be added in the observation as per his birth certificate or other legal name change document not his other country X passport in accordance with article 2.13 which states that the full name should be added as an observation, evidenced by their supporting documents, in line with normal policy.
6.14 However, HMPO retains the right to use the passport observation page to include any information considered relevant to assist in the identity of the passport holder” (So long as this does not lead to discrimination between UK nationals (single and dual nationals)! Dual nationality is not one of the pieces of information considered relevant by the HMPO since not all dual nationals including myself have their names mentioned as dual nationals in the observation page of the UK passport.
From the above articles it is clear to me that this has nothing to do with security but rather to assist the passport holder in justifying to various authorities in country X or any other country where you were a resident that you have other official documents including school certificates, medical certificates, university diplomas etc. that may be issued under a different name, and you need to show the authorities that you are the same person. Unfortunately, the way the HMPO is going about it is discriminatory and may expose the UK passport holder to unnecessary risk. To be quite frank, mentioning a British Citizen in his UK passport his country X nationality is hardly an observation of the UK passport holder (a scar is an observation). The HMPO have confirmed that reference to dual nationality will not be mentioned as an observation.
@DoctorAllcome with regards to your reply “If you leave the U.K. on a British passport, and get arrested or detained in another country where you are also a citizen you are not viewed by international law as 100% British. That was not decided by any one country, but by the United Nations democratically. You can dislike this all you want, but it is fact”. I am in full agreement with this. International law have only stated what is natural. When I am in country X I consider myself a 100% citizen of country X and likewise when I am in the UK I consider myself 100% British. This is what dual citizenship is about!