Current practice in the Diocese of London is that checks are required for all Church of England clergy from outside of the diocese who are invited to officiate (including preaching) within the diocese. This normally consists of the Area/Diocesan Bishop requesting a Clergy Current Status Letter (CCSL) from the Bishop in the diocese where the clergy person currently holds a license or permission to officiate. This is to confirm that the clergy person is in good standing and includes a safeguarding check from the Diocesan Safeguarding Advisor to ensure that DBS checks and training are up to date.
All Anglican Communion clergy ordained outside of the Church of England or the Church in Wales require the written permission of the relevant Archbishop to exercise ministry in the Church of England, even as a ‘one-off’. Applications are made by the diocese in which the clergy person wishes to officiate; they will also check that DBS checks and safeguarding training or their national equivalent are up-to-date, and that the applicant has the legal right to remain in the UK.
Canon B43 covers clergy from other denominations. In brief, assurance needs to be sought from the minister’s authorizing body that they are in good standing and up to date with DBS checks and safeguarding training. There are different levels of permission depending on what they are being asked to do: some things can be done without consultation or permission; others require consultation with the PCC and the permission of the Bishop.
It would ordinarily be the Incumbent or Priest-in-Charge who would liaise with the Bishop in connection with such matters.
During a parish vacancy this information would be shared by the Bishop or Archdeacon as part of the vacancy process.