Why Did it Take the Americans to Unmask Jihadi John?

choi

Emma Glanfield, Why Did it Take the Americans to Unmask Jihadi John?  Daily Mail, Feb 26, 2015.
www.dailymail.co.uk/news/article ... e-confirm-name.html

Note:
(a) jihardi (n; jihad +‎ -i [qv; which can be a suffix denoting plural form in Latin, Italian AND Arabic], after Arabic jihādī; plural jihadis): "jihadist"
en.wiktionary.org/wiki/jihadi

(i) But Collins dictionary lists a second plural form "jihadeen"
www.collinsdictionary.com/dictionary/english/jihadi
(ii) The same as in
mujahideen (n; Arabic mujāhidīn, plural of mujāhid, literally, person who wages jihad; First Known Use 1887)
www.merriam-webster.com/dictionary/mujahideen

I can not find the singular form of mujahideen in ENGLISH.

(b) "while Whitehall sources confirmed Emwazi had been known to security services for several weeks, the Home Office would not release any confirmation of his identity.

The "sources" may be confidential, on background. And "Home Office" clearly means the official position of the government.