Oops, I should have said 12th March 2016. I have always been reluctant to put this sighting on as I couldn't be 100% sure it was definitely 17517326 (even if it's definitely not 17517324; no photos available of 326). I've re-uploaded my photo but the quality is poor and there's a telegraph pole in the way. But it's definitely the same machine pictured at Meldon on 30th September 2018 on the Flickr site linked above.
I hope it's OK to link to an external site but is this picture this machine? https://www.flickr.com/photos/kimctomcat/43360589720/in/photostream/
I saw this at Meldon on 12th April 2016 and know that because of the rusty grille of the engine compartment behind the cab door. Definitely not http://www.ontrackplant.com/road-railers/view/2762 for the same reason.
An LH Skyboom with instruction stickers in English is currently being advertised for sale in Poland, being labelled for "Tor Rent" who I understand to be a Polish RRV operator. I believe this is either this vehicle or sister FR1316.