London - British gun owners had until midnight last night to surrender tens of thousands of handguns outlawed following the Dunblane massacre last year of 16 schoolchildren and their teacher. Under new laws, hailed by the government as among the toughest firearms legislation in the world, all handguns over .22 calibre must be given in to police or their owners risk jail sentences of up to 10 years. Meanwhile in Canberra, Australian gunowners rushed to hand in newly-outlawed weapons yesterday before a deadline expired at midnight for a nationwide amnesty and gun buy-back.