Join Date: Sep 2005
Location: HEL
Programs: AY Platinum, TK Elite, BT Executive, AA, BA, SK, DL, NT, WB + hotels
Posts: 10,265
This is not at all as complicated as it sounds.
At LHR, you will go through security. No passport control.
At HEL, you will go through immigration. No security control. 55 min should be just fine.
At RVN, you will pick up your bags and be on your way. No controls.
Please check your departure airport in NYC since La Guardia is a domestic-only airport.