ILR: Is letter from previous employer required????

I'm a work permit holder. I came to UK during Sep 2004 and soon I'll be applying (PEO) for indefinite leave to remain on completing 5 years’ continuous stay in the UK as a work permit holder. I switched to a different employer around 3 years back and got my work permit transferred to my new employer that time.
By reading the Set(O) application form and guidance form, I understand that I don't need to submit any letter from my previous employer for my ILR application. Please could you confirm whether my understanding is correct. I'm confused because in the forums, members have indicated that they have been asked to produce the letter from the previous employer at PEO office esp Croydon. My previous employer doesn't has a policy of giving out such letters.
Your responses are much appreciated.
Thanks.