Please be aware that London has multiple airports and that these results are only for City airport.
The best month to arrive at London is October and the most expensive month to fly is September. (Average prices, based on 221 datapoints.)
The best day to arrive at London is Wednesday and it would be best to avoid Friday, as prices are on average 64.8% higher than on Wednesday. (Average prices, based on 234 datapoints.)
At London the most flights depart around 17:00. (Hourly flights, based on 269 datapoints.)