On a web site such as this I should be careful not to claim to speak for The Baroness Warnock I don't .
Warnock et. al. established a logical basis for the justification of embryo research and this can be extended to related fields.
So far as I am concerned the whole matter revolves around the concept of Original Sin.
Thus I begin my account of this matter with the pontifications of Pope Pious IX in around 1854 on the Immaculate conception of Mary the Mother of God.
It does seem that the dispute at the time revolved around the significance of baptism. The point appears to have been that Mary conceived Jesus before John the Baptist began baptising and so how could she be a fit vessel for the development of Jesus' earthly body?
Firstly, what is the purpose of baptism? Baptism is a process under which the assembly - and especially the God Parents - vow to protect the child from Original Sin and signify this renunciation on the part of the child by the washing away of all trace of original sin.
Secondly, What is Original Sin? Original Sin is the Sin of Adam. The Sin of Adam - the cause his being driven out of the Garden of Eden - was the eating of the Fruit of the Tree of Knowledge. What the? Basically for mid 19th Century clerics - Mendel first published on genetics in 1866 12 years after Pious IX - nature was in a state of Grace and mankind was forever messing up the natural order of things with his steam engines and such.
A lot of people think that original sin is to do with having sex. Quite a few people think that Adam stuck one on Eve and that's why they got evicted. This is entirely wrong. However, sex does provide the prime example of original sin for the 20th Century Roman Catholic Church. Essentially the 19th century Roman Catholic Church were anti Industrial pastoralists and so were the Anglicans. All yer ancient churches are evenly distributed across the country but yer- newly built in the 19th Century Methodist chapels were concentrated in densely populated urban industrial areas.
So, if it happened in 'Nature' for which read 'on the farm' it was part of God's Grand Plan for the Universe but if it didn't happen on the farm it wasn't. Farm animals have sex and get pregnant so it was OK for people - the people the celibate priests 'farmed' - to have sex and get pregnant. Sex not a part of Original Sin. However, farm animals do not use contraception and so contraception was not seen as a part of God's Plan. It was seen as mankind getting away from the script and being too clever by half - Original Sin.
From Mendle on though study of God's Vast Eternal Plan extended out of the farm yard into the big wide world and also around the mid 19th Century dinosaur and other fossils were discovered and very gradually 'the wild places' were seen as God's Eden Mankind had been driven out of instead of the farmstead being seen as Islands of Heaven terraformed in a wilderness by the providence of God.
Thus many people began to study simians as precursors to Mankind. The idea that it was chimps and not swans that God put on earth for us to build our societies upon.
However, once we study nature as opposed to farm husbandry we find animals - insecty types - where the female takes a solid package of sperm - a spermatophore - and carries it around unopened and chucks it away and replaces it if a better prospect appears and only opens it and fertilises her eggs with it when the time is right.
What Pious IX decided was:that Mary's parents created her body in the normal way BUT BEFORE HER SOUL COULD ENTER IT it was transformed to make it impervious to original sin.
As sort of outlined above, Original Sin is thinking for yourself and not accepting your 'place' in the Order of Things. Thus Pious IX may have been thinking that Mary the Mother of God was Pure Love in the terms of the day a Mongol, in today's terms Downers Syndrome.
The Important point here is that Pious IX enshrined in Roman Catholic belief the idea that bodies are made and souls enter them. that there is an intervening period .
The second element in this is PURE LOGIC.
We know about identical twins. We know that they result from one zygote - the stage after egg and before embryo - splitting into two. We know that souls are indivisible. A pair of identical twins have much in common but they are individual souls capable of independent life.
Thusly, The soul does not enter the body at fertilisation and it cannot enter at any stage whist the splitting into twins is possible so we KNOW that the soul cannot enter the body before Implantation - into the wall of the womb.
Thus, when we manipulate embryos and stem cells we are not dealing with life but with material which has little greater Potential for Life that the eggs most women regularly shed in their monthly cycle.
Thus, to sum this up in technical terms:
Whenever a new idea comes along we have to challenge it. We have to decide whether it is hubris or revelation.
In other words. Some would stop the clock on human development by saying that on his one visit to earth Jesus had the Last Word on everything. But, clearly, we all explain things differently to a two year old from how we later re-present that thing to the same child when they are six
Revelation continues but we do not doubt the Word of God when we use scientific method to test new ideas to check whether this new idea is hubris or revelation.