Repointing advice

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Hi all

I have a property built in approximately 1910 using "Ruabon Red" brick which needs some areas of repointing.

Can anyone give me a clue as to what mortar needs to be used?

My understanding is that hydraulic lime mortar should be used to aid breathability as the property is solid wall construction but there seems to be plenty of people who say that Portland cement will do.

Thanks.

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Thanks for your input everyone, the link to the old houses forum was very useful too.