For those caught in a similar catch-22 situation, namely:
Recently naturalised in married name (or other new name);
AND documents including foreign passport held in maiden name (or other previous name);
AND HM PO refusing or delaying first British passport (citing as their reason, "to avoid the creation of a
second identity")
Summary of Options
1) You are:
Non-dual national - UK citizen (only)
You hold an uncancelled foreign passport in different name
(eg passport is in maiden name but you have been recently naturalised in UK & now applying for British passport in married name)
a) Cancel/surrender or revoke the foreign passport
PLUS obtain letter or certificate of cancellation (if possible)
b) Change name on foreign passport (to match name used in UK)
Note: this is often suggested by HM PO but can't easily be done if holder is no longer a citizen of the foreign country;
(eg typically due to losing foreign citizenship due to granting of UK naturalisation)
c) Apply in married name plus request an official observation in British passport to record use of maiden name
(possible option for professionals, members of nobility & similar cases - proof required)
d) Revert to using maiden name (or previous name) in UK & (re-)apply for British passport in the maiden/previous name;
(proof of reverting to full use of the maiden/previous name in UK will be required by HM PO)
e) Reapply/reacquire your original nationality (and reobtain a foreign passport); then obtain UK 'Right of Abode';
(as per option in group 2 below)
2) You are:
Dual national - with UK citizenship plus 1 or more other citizenships held
You hold an uncancelled foreign passport in a different name
(eg maiden name & you have been recently naturalised in UK, now applying for British passport in married name)
a) Revoke foreign citizenship; (see options in group 1, above)
b) Cancel/surrender or revoke foreign passport
PLUS obtain letter or certificate of cancellation (if possible)
c) Change name on foreign passport to match name used in UK
May involve trip back to country if the local embassy (in UK) cannot do this.
Minor name differences (eg just forename)
may be accepted by HM PO;
d) Apply in married name plus request an official observation in British passport to record your use of maiden name
(possible option for professionals, members of nobility & similar cases - proof required)
e) Revert to using maiden name (or previous name) in UK & (re-)apply for British passport in maiden (/previous) name;
(proof of reverting to fully use the maiden/previous name in UK will be required by HM PO)
f) Give up on applying for/receiving British passport; apply for Right of Abode (a sticker in your foreign passport)
Note: RoA only granted if no British passport is held
Pros: proves your right of abode in UK;
Cons: costly; no additional travel benefits; expires with foreign passport (so need to renew & pay again);
Unclear if RoA adequately proves right to access UK NHS
Notes per country:
India - catch-22:
dual nationality not recognised;
it's hard to cancel/surrender or update India passport without first obtaining a British passport
&
British passport may be withheld until India passport is changed (!)
Note: Some posters have reported HM PO have accepted a letter committing to change name in the IN passport asap;
British passport has then been issued on that basis
Iran - catch-22: reported that wives (only?) cannot change to or use a foreign name
Philippines - 'cancel passport' option successfully done via UK embassy;
AND obtained Certificate of Cancellation for small fee (£18--) to use as supporting evidence
ie confirmation from embassy that holder lost citizenship from date of UK naturalisation
AND so is ineligible to hold PH passport
AND PH passport was invalidated by UK naturalisation
Russia - dual nationality seems to becoming a sensitive topic;
recent Russian laws appear to require foreign citizenship to be reported to the authorities (at least for residents in Russia);
- may be harder to approach embassy for supporting documents
Notes: some posters have reported they are currently in progress with filing name changes in their country (or via a UK embassy);
news on outcomes awaited
1 poster is currently in progress with applying for 1st British passport in a
previous name to that used for their naturalisation.
news on outcome awaited
Other options...
Complaints to HM PO
[some made; outcomes unclear]
Legal/other challenges to new policy
eg via campaign group, migrants group (or similar) or via MP
[unaware of any being made at present]
Hope this summary helps someone - good luck to all.