Lark
The lark was a development of the Hoover model 115. As John said there were two models, the 12 and the 14. I understand that the (earlier) 12 has a more direct relationship to the 115 as it used the same brushroll, the 14 had a wider brushroll (possibly from 61 series) although I believe the mechanicals are the same, as was teh styling - the models shown above are both 14s.
They are comparativly rare models and, although I understand they were made in the UK (as possibly was the 115), they were not sold here, we has the 115 (actually 119 and later 1224) version here from 1951 until 1958 until the introduction of the all new 1334, which looks rather like the green model behind the Lark in John's photo above