Interesting story at Heathrow... Frightener took off and the Air controller launched a Trident, thinking the Frightener would have turned to give the "split" (one going north, one going south). Unfortunately, the Frightener was only doing about 90 kts with the Trident hurtling up behind. Air man said to the Frightener: "Would you move over to the right, traffic to come past"... which it did.. and both went merrily on their ways!! Happy days...