If you drive through the tunnel under the A24 from Basthorst, you'll find yourself at a dead end. I was already familiar with this from previous tours.
You can only return in a loop because the Steinau River borders the area.
There is no official road to Lanken here, nor is there a bridge over the Steinau River.
You can only ford the Steinau River, which is neither wide nor deep here.
There are stones in the stream every now and then that you can use to cross by pushing your bike through the stream and leaning on them.
But that's not for everyone, and everyone has to decide for themselves whether they want to take it on.
The path to the Steinau River leads across fields, along tractor tracks, or along the edge of the fields - you can't really cycle, or only moderately so - pushing is better.
The banks of the Steinau River are muddy in places, and the tall nettles on both banks are particularly uncomfortable in shorts.
But it's possible - I made it over to Lanken today without getting my feet wet.
In winter, when it's frosty and the muddy ground is frozen, it's easier to get through here. I managed to do it a few years ago, on foot, parallel to the A24 through the forest toward Wildbrücke, in frost.
This route today is the extreme variant, and really not suitable for following. The farmer certainly doesn't like it when you drive or walk along his fields. So please, no complaints if someone tries it - it's at your own risk, no guarantees, and if you do, it's better to do it in winter when it's frosty. 😉