I was told years ago that if you don't put Kings down 1st place then you aren't considered for 2nd place

My son is 21 and when even when he went to Secondary School it was illegal to use the method you describe. So you really must be talking about a long time ago.

In line with the School Admissions Code (2014) we operate an equal preference with ranking system.

This is a national model designed to ensure, as far as possible, parent/carers' preferences for particular schools are considered fairly, equitably and consistently.

Equal preference requires the admission authority to consider all preferences received for a particular school (first, second, third, fourth and fifth) equally and, where the school is oversubscribed, apply the oversubscription criteria. Where more than one preference can be met the local authority will offer the highest ranking preference.

Main risk is that if you don't put it first then you may well be given your first choice place (after all that is the one you want) and not be considered for a place at Kings

We no longer use a system where schools prioritise applications that list their school as first preference; instead we use an equal preference system. This means we pass on your application data to your preferred schools, but do not tell them the order you have listed them.
Only we know your order of preference. If multiple schools inform us that they can offer your child a place, we will offer you the highest preference available. You will not receive multiple offers.

Parental Preference
It is essential to rank your preferred schools in the order you would like them to be offered. Schools will consider all children equally, as they do not know if they have listed them as first, second or third preference. Each school applies its own admission policy looking at factors such as siblings, religion, distance and ability or aptitude where applicable. This means when schools rank applicants, they will not disadvantage anyone who has names them as a second or third preference. It is possible for you to receive an offer of a place at a school listed as your second preference before another parent who names it as their first if your application has higher priority under the schools' oversubscription criteria.