Possible Clues:

• Hooligan caught by CCTV and alarm
• Member of a Germanic people who ravaged Rome in 455
• One may deface a building
• Graffitist, to some
• One maliciously damaging vehicle, youth going north
• Destructive type left at rear of London museum
• Smashing individual, say, in line behind museum
• Wanton wrecker
• One wrecking vehicle young chap's driven up
• Museum initially lambasting hooligan