Book of Common Prayer (page 195)

The Common of Saints

The festival of a saint is observed in accordance with the rules of
precedence set forth in the Calendar of the Church year.
At the discretion of the Celebrant, and as appropriate, any of the
following Collects, with one of the corresponding sets of Psalms and
Lessons, may be used

a) at the commemoration of a saint listed in the Calendar for which no
Proper is provided in this Book

b) at the patronal festival or commemoration of a saint not listed in
the Calendar.

Of a Martyr

Almighty God, who didst give thy servant N boldness to
confess the Name of our Savior Jesus Christ before the rulers
of this world, and courage to die for this faith: Grant that we
may always be ready to give a reason for the hope that is in
us, and to suffer gladly for the sake of the same our Lord
Jesus Christ; who liveth and reigneth with thee and the Holy
Spirit, one God, for ever and ever. Amen.

or this

O Almighty God, by whose grace and power thy holy martyr
N triumphed over suffering and was faithful even unto
death: Grant us, who now remember him with thanksgiving,
to be so faithful in our witness to thee in this world, that we
may receive with him the crown of life; through Jesus Christ
our Lord, who liveth and reigneth with thee and the Holy
Spirit, one God, for ever and ever. Amen.

or the following