thanks for catching that, Winniesboy. You are right. The Echo arrived in the Shield’s area on April 10 from points south where it was assisting the Haixun.
As far as I can tell from searching articles, the oil slick was first spotted on the evening of the 13th - so three days after the Echo arrived, but it is said not from the Shield or from the Echo.
“In anything like this I am very conscious, I have 20 years experience of trying to find things on the seabed, it’s pretty much my day job."