(S (S (NP (BASENP (DT An) (JJ 18-year-old) (NNP UK) (NN student)) (VP (VBN suspected) (PP (IN of) (S (VP (VP (VBG throwing) (BASENP (DT a) (NN fire) (NN extinguisher))) (PP (IN from) (NP (BASENP (DT the) (NN roof)) (PP (IN of) (NP (NP (BASENP (DT the) (NNS headquarters)) (PP (IN of) (NP (BASENP (DT the) (NNP Conservative) (NNP Party)) (PRN (LRB -LRB-) (QT (DQL `) (BASENP (NNPS Tories)) (DQR ')) (RRB -RRB-))))) (PRN (COMMA ,) (NP (BASENP (NN 30) (NNP Millbank)) (COMMA ,) (BASENP (NNP London))) (COMMA ,))))))))))) (VP (VBD was) (VP (VBN arrested) (PP (IN on) (BASENP (NNP Monday)))))) (PERIOD .))