london suicide attack pop concert manchester kill 22 people may might prevent security service respond differently intelligence months attack government report find salman abedi 22-year-old briton bear libyan parent blow end show u.s. singer ariana grande deadly militant attack britain 12 years victims include seven children government-commissioned report david anderson former independent reviewer terrorism legislation find security service pass two piece information bomber early year report say security service consider intelligence terror-related time say highly relevant conceivable manchester attack particular might avert card fall differently report say find follow review roles security service four attack london manchester march june year leave 36 innocent people dead three six attackers know security service person active investigation report say overall say britain security service perform well amid grow threat islamist militants purpose internal review report cast apportion blame though investigative action part sound many learn point emerge report say britain thwart nine plot last 12 months prime minister theresa may spokesman say tuesday interior minister amber rudd tell parliament intelligence service counter-terrorism police currently carry 500 live investigations third since begin year investigate 3,000 people review find abedi one small group former suspect interest britain security service consider investigate meet due hold discuss potential threat may 31 nine days attack manchester arena britain say 'conceivable manchester attack might stop