Droitwich uses two metre-high ceramic and metal valves, 
     which are no longer made.

said valves: https://www.radiorewind.co.uk/images/1983027.jpg https://www.radiorewind.co.uk/images/1983023.jpg

from: https://www.radiorewind.co.uk/radio1/droitwich.htm

https://i0.wp.com/www.richardmudhar.com/blog/wp-content/uplo...