Restriction in deed apparently preventing land transfer

In order to settle a boundary issue with my neighbour I'm in the process of selling said neighbour a strip of my garden and surrendering access rights I have over a bit of their property. My neighbour's conveyancer is preparing all the paperwork (TP1 and deed of release) but is currently claiming that a restriction in my deeds is preventing the transfer from going ahead:

"Unfortunately I need the Land Registry to remove the entry as they will not register the transfer and surrender until the restriction is removed." (Quote from my neighbour's conveyancer)  

The wording of the restriction in question...

"No disposition of the registered estate by the proprietor of the registered estate [me] is to be registered without a written consent signed by [my relative] or her conveyancer" (From my deed)

...seems to indicate that the written consent of my relative would be sufficient, but the conveyancer insists this is not the case, and the restriction must be removed if the transfer is to go ahead.

Is what I'm being told accurate or would "written consent" suffice in this situation?

Any advice would be greatly appreciated.  

Tim - if the restriction 'bites', and it does as a transfer is a disposition, then you either need the consent or the restriction cancelled/withdrawn as appropriate.
I suspect, but perhaps ask them to confirm, that whilst a written consent will enable the transfer to happen are they perhaps concerned that the restriction will be carried forward to their client's new title
If they are then it would be prudent to obtain the written consent and ask the restrictioner to also include a statement to confirm that it should not be carried forward to the new owner's title.

HM Land Registry public guidance - GOV.UK (www.gov.uk) - have your say to help us to improve the support we provide 
 

Thank you, Adam. That's good to know.