Pronunciation of 'Ellen'

zyc50

In his biography of Mountbatten, Philip Ziegler writes:

\"His first fond memory was of his nurse, a Welsh woman named Ellen
Hughes. Dickie called her 'Ennen', because the double 'l' was
difficult to pronounce.\"

Producing what should be /l/ as /n/ I can understand: small French
children do it too. What I don't understand is the mention of a
'double l' being specially difficult. As far as I know, the double
'l' is purely a spelling convention, and doesn't represent a sound
different from the consonant shown as a single 'l' in 'Helen'.

Do you think that Philip Ziegler is here alluding to the special Welsh
\"double l\", or that there's a confusion between sounds and their
written representation?