So where exactly was Holy Trinity Priory?

This rather interesting article shows that it was in the south-eastern part of Christchurch Park, possibly exactly under the Mansion? The “Withypoll slab” of Tournai marble, which seems to lie near the back gardens of Bolton Lane, may be a significant clue – note how Edmund Withypoll behaved rather like the Stanleys against the Harringtons in his dealings with William Dandy or Daundy. It also explains why St. Margaret’s Church was constructed as a chapel of relief (overflow) to the Norman era Priory, which was then demolished or superseded.

Thanks also to the late John Blatchly and to Sir Diarmaid MacCullough for their 1977 research. There is a July 2019 update as well, from Ipswich Borough Council.