Old Vine Registry (OVR) is a non commercial voluntary and community-based registry  which has 10000+ entries of old vineyards worldwide. Vineyards must be 35+ years old. 

Thomas Walk Vineyard is registred with Old Vine Registry. The registry reveals that Thomas Walk Vineyard is the oldest in 2 ways -  see extract from OVR below:

Thomas Walk Vineyard is the longest standing vineyard in Ireland. The first Rondo vines were planted in 1985. Besides research plantations in Continental Europe Thomas Walk Vineyard seems to be the oldest Rondo plantation worldwide. Note: The Rondo grapes was registered with the German Federal Office's Varieties Register in 1997. Prior to 1997 it carried the Geisenheim Research Institut breeding number Gm 6494-5.

Click on picture below to go to the Old Vine Registry