? Mystery Call at Corner Hall

On leaving work at about 6.50pm I heard a call a few times that I have heard a couple of times before here, at this time of year a previous year, & in the afternoon. I looked up straight away but my view towards the call was obscured by the offices. The best way I can think to describe it is that each call sounds like an individual note of a Green Woodpecker's 'yaffle' & slightly reminiscent of a Jackdaw's 'jack' call but less 'snappy' & more 'sqwarky'. My suspicions are that it is a RING-NECKED PARAKEET, which I do see in Hemel in the Autumn occasionally, I have heard them make a Green Woodpecker-like sound before, & there is likely favoured habitat nearby to my office. I'll just have to keep my eyes & ears peeled to nail it next time & get it on my work list.