The "Alexei" from UKName: Nikolai Chebotarev (d. 1987)
Recent claims are made in the book, "Blood Relative", by British history professor Michael Gray that the Tsarevich (from whom he claims illegitimate descent) escaped Russia with the Dowager Empress in 1919 onboard HMS Marlborough, and assumed the name Nikolai Chebotarev.
(...) Nikolai Chebotarev never publicly claimed to be the Tsarevich in his lifetime and so far no attempt has been made or contemplated to exhume his remains to perform DNA tests which would, unlike Mr. Gray's claims, resolve the matter with 100% certainty.
(...) a host of unsubstantiated conspiracy theories involving forensic evidence tampering, combined with a loose (in places erroneous) interpretation of DNA analysis, advanced in a futile attempt to explain alleged body switch and DNA results which do not prove his point.
From:
http://www.serfes.org/royal/romanovpretenders.htm Michael Gray is not the author's real name. His real name is William Lloyd Lavery and he claims to be the illegitimate son of Nikolai Chebotarev ("Alexei") and princess Marina, Duchess of Kent.
More info:
http://media.dagospia.com/public_html/articolo_2272.html (site in Italian and with some nudity).