The world's oldest monarch who is none other than Britain's Queen Elizabeth turned 90 on Thursday.  Her birthday will be heralded with beacons and gun salutes. The queen is still an energetic lady who performs hundreds of engagements a year and shows no signs of losing her appetite for the job. Usually her birthday passes with little ceremony.  But this time, being the 90th, birthday will be celebrated in a special way; Elizabeth will greet well-wishers near her Windsor Castle home, west of London, and later light a beacon, the first of 1,000 to be lit across the country and worldwide to mark the occasion.