scotland yard. four men detained as part of an ongoing investigation into islamist related terrorism. the men were allegedly plotting to carry out attacks on british soil. fears of an attack here rising since britain joined the u.s. in bombing isis targets in ooh rack. security on high alert. >> in that sense, it's probably the biggest security operation in the world. >> her majesty the queen lays her wreath. >> reporter: her majesty leading her country in the remembrance of the fallen since world war i. members of the royal family in tow. noticeably absent, prince harry who secretly returned to afghanistan for a quick trip to represent the queen and pay his respects. the royal family's show of solidarity and appreciation from the crowd. >> applause. i never heard that before here