I'm still not convinced that HMRC's interpretation of s20, namely
that all gifts to any one individual in any tax year must be
totalled, and if the aggregate value exceeds £250, then none of
the gifts making up the aggregate count as "small", even if there
exists a subset of those gifts, the aggregate value of which is
not more than £250 (in which case that subset should qualify as
"small" with the remainder not qualifying), is justified by the
wording in IHTA84.

But leaving that issue aside, what would their interpretation be
if two gifts had been made in one tax year, of let's say £150 each,
but with the first gift having been made more than 7 years before
the relevant date of death, and the second gift less than 7 years
before death?

In other words I'm looking at that tax year which straddles, and so
is divided into two parts by, the beginning of the 7-year period.

One gift was made in the first part of the tax year, the other in the
second.  The first gift will in any case be too old to be considered
for adding back into the estate.  The question is about the status of
the second gift.  Is it "small" because it is the only gift to a
particular person in a particular tax year *which is eligible for
inclusion*, or is it "not small" because, taken with the first gift
*even though the first gift is ineligible for inclusion*, it brings
the total of gifts to that person in that tax year to £300?