I was at LHR on Tuesday April 17th. Two men were sitting there on their chairs and predicted any incoming aircraft. I asked them about what they're doing. They had a printed chronological list of every arriving plane which they got from the internet, a scanner with earplugs and a lot of experience and knowledge. They also had folders with every airline fleet in there. So they checked registrations and noted it down and checked if they'd already seen it I think. Just ask people there, those men were very friendly and gave me a lot of info during the day.
Bring it back, bring it back, bring it back