The G8 summit at Gleneagles in 2005 was deemed a top terror target but experts believed an attack on London was more likely, newly-released files show.
Officials' chilling warning horrifically came true when Islamist extremists struck the capital instead of the remote Scottish town, killing 52 people.
Eight world leaders including Prime Minister Tony Blair, US President George Bush and Russian premier Vladimir Putin met at Gleneagles 15 years ago.
Issues including climate change and the plight of some African nations topped the agenda. The high-profile, three-day event was marred by protests at nearby Auchterarder and in Edinburgh, which included violent clashes with police.
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