While recently working a lot from the ground I have revisited the aikido notion of “extension”.
Extension for me is the sense of “bringing myself fully to the meeting”. It is both approaching and opening to my partner. It has something of Gestalt Therapy’s coming to the “contact boundary”.
Extension is what procduces the possibility of cohesiveness in the ki-musubi or the blending.
The active and receptive quality of extension transforms the contact from arbitary grabs and pressures into a unified yet morphing stream of evolving contact.
It is this that contributes my experience of the expansion time in practice. Our encounter moves from a sequence of stuttering moments into into one elongated pervasive sweep!
Strangley the sense and necessity of extension becomes for me more acute when contacting my partner from the ground.Working on the ground highlights the necessity for me to bring my whole body torso and head as well as limbs into a vital quality of extension so that that no contact is arbitary or subsiduary.
FREEFORMING 
For me, the feeling of extension is one of the most exciting aspects of aikido practice. I am particularly interested in the way that partners are often able to join in with each other before physical contact has happened and how a mutual comittment (to continuing the attack, to continuing to join in), is neccessary in order that aikido can happen.
In my experience, although the physical possibilities (in terms of the shapes that are made) are fairly limited, the continuity of the sequence of shapes, or the patterns are not. This I think reflects the escence of extension in that it provides a fluidity to otherwise solid set pieces, and opens up new avenues that may not otherwise have been possible to access.
This is why I think it’s one of the more exciting aspects of practice.
I hope I can get up to London soon and join in with you guys.
Cheers