(S (S (BASENP (NNS Police)) (VP (VBP are) (VP (VBG reviewing) (NP (BASENP (JJ major) (NNS events)) (SBAR (S (VP (TO to) (VP (VB be) (VP (VP (VBN held) (PP (IN in) (BASENP (NNP London)))) (PP (IN over) (BASENP (DT the) (NN weekend)))))))))))) (PERIOD .))