(S (S (PP (IN In) (SBAR (WHNP (WP what)) (S (BASENP (NNS police)) (VP (VB believe) (SBAR (S (VP (VBZ is) (NP (BASENP (DT the) (JJS second-largest) (NN heist)) (PP (IN in) (BASENP (NNP Britain))))))))))) (COMMA ,) (S (BASENP (JJ armed) (NNS robbers)) (VP (VP (VP (VBZ stole) (BASENP (QP (RB almost) (SHARP #) (NN 40) (NN million)))) (PP (IN from) (BASENP (DT a) (NNP London) (NN jewellery) (NN shop)))) (PP (IN on) (BASENP (NNP August) (NN 6)))))) (PERIOD .))