Who was Cardinal Antonelli and what was he?

Dear Chas, 

Cardinal Giacomo Antonelli (1808-1876) was a Vatican diplomat and
Secretary of State at the time of the Risorgimento (Italian
Unification), and was involved actively against the unification of
Italy, staying "prisoner" at the Vatican with Pope Pius IX after the
Italians united, in 1870.

See an online biography by Frank J. Coppa : 
Frank J. Coppa , "Antonelli, Cardinal Giacomo (1808-1876)", The
Encyclopedia of 1848 Revolutions,
<http://www.ohiou.edu/~Chastain/ac/anton.htm>.

See also a letter he wrote during the American Civil War, trying to
bring to negotiation (1864):
Letter of Cardinal Antonelli to CSA Commissioners
<http://jmgainor.homestead.com/files/PU/MDPC/LA/cwn/ca-csac.htm> 

His meetings and discussions with Lord Russell: 
Dispatches from Rome to Lord Russell and the Earl of Clarendon, from
Odo Russell (1858-1870).
<http://www.reformation.org/dispatches_from_rome.html> 

CATHOLIC ENCYCLOPEDIA: Giacomo Antonelli (1911)
<http://www.newadvent.org/cathen/01583d.htm> 

A picture of him: Cardinal Antonelli., from Kings of Italy and Popes
collection.  Elibron Classics, 2001
<http://www.elibron.com/english/other/img_detail.phtml?msg_id=72120> 


Of course, there is a less famous Cardinal, whose name is Antonelli: 

The Cardinal of Florence (Firenze), Italy (b. 1936)
<http://www.catholic-hierarchy.org/bishop/bantonelli.html>

I hope this answered your question. My search terms were his name in variations: 
<://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=%22Cardinal+Antonelli+%22>
(for much mroe links)

Please contact me if you need any clarification on this answer before you rate it.

I believe this Cardinal never took Holy Orders