“she is rock steady off the lead (the dog not my wife)”.
Please can you offer some advice on how you managed this?
I am sure many others would wish to know……

Hi Foxyboy......I'll add the entire paragraph that you refer to and then explain.....
"However - there is a small minority of 100% working bred teckels that are less independant and less gung-ho- death or glory- driven. We own just one. She has predominantly German dam line von Rauhenstein and vom Linteler-forst (good lines) and Italian/Scandi sire line. But........here's the thing, she is my wifes country companion as my wife wanted one dog that she could walk off lead without it going free-lance - so we didn't allow it the enjoyment of hunting and at 2.5 years she is rock steady off the lead (the dog not my wife)"
From our experience, not huge compared to some, but having owned dachshunds since 2009 and having owned 9 in total - 2 show-bred - 6 working-bred and 1 show/work combination I believe the steadiness of 'Mia' the bitch in question is chiefly due to..
(a) We know the breeder well, and specifically asked for a soft-natured bitch prior to their birth. Having weekly updates, we chose 'Mia' as she seemed to be balanced and level headed - from what you can tell in the first 3 months.
(b) Her Italian/Scandi lines are generally not too hardcore and even some of the German dogs in the pedigree are relatively easy-going.
But the main reason - as mentioned in the paragraph is...
(c) We did not encourage her to hunt at all during her obedience training. In fact we discouraged her and we avoided areas of high concentration of game (we are surrounded by game-shoots and also a very high hare population). Even with zero encouragement, she will happily flush game from hedges if we are walking past them but she will not chase low birds after flushing and she won't go off looking for game on a walk, she stays within sight of my wife all of the time and if she dips into a hedge or wood, she is keen to come out and regain sight of my wife. This latter behaviour is a combination of nature and nurture - a softer, less independent genetic material combined with strict training and zero encouragement.
The pup in the most recent video 'Gem' is, by design, again less independent and driven due to her breeding and...so far...she is exactly as expected and hoped.....fingers crossed, it's still early days.