I wonder if anyone can help.

I've created and published an evaluation form which has a lookup field to my delegates table. I'd like in the email I send to include a url so that when they click on it it automatically selects their delegate record in the delegate lookup field.

I just can't seem to get this to work. Not having any difficulties passing data through urls to place into normal text and date fields, but can't get it to work with lookup fields. 

I thought it might be that I needed to use the delegate's zoho ID so I've been trying with this url

https://creator.zohopublic.com/creativeducation/eep/form-perma/Evaluations/XdjAbJ3g7rH0k4CP0G8NaYypwP4KTeZPx99jOSBdfWJd32xXzV8PJqPUqAj2F2dhaywkSrtgwxODH4UK1XM07UfYUPyY9uZmPhBx?Delegate=619509000000167036

All help appreciated at this stage!

Tom