By email, I have recived news that on the feast of the Immaculate Conception (this Saturday 8 December) at 2pm, a group will gather to pray the Rosary in reparation, in front of the offensive painting. This is intended as peaceful witness to pray "as much of the Rosary as we can before being asked to leave."
I can't imagine why the authorities should ask people to leave. This kind of "art" is intended to provoke a reaction from ordinary viewers. Surly nobody is going to exercise any authority would want to rule out reparative prayer as a reaction? I would suggest that people have their mobiles and cameras ready in case anything like this happens.
If you want to join in, assemble in the Sunley Room (in the main building) shortly before 2pm. Remember that you need to deposit bags/umbrellas in the cloakroom.
If you can, please complain in writing to the Director, Nicholas Penny, at The National Gallery, Trafalgar Square, London WC2N 5DN or email@example.com
The email also carried this prayer of Wiseman which is said as part of the Prayer for England on the third Saturday of the month. Always worth reposting:
O most loving Lord Jesus, Who, hanging on the Cross, didst commend us all in the person of Thy disciple John, to Thy most sweet Mother, that we might find in her our refuge, our solace, and our hope; look graciously upon our beloved country, and on those who are bereaved of so powerful a patronage; that, acknowledging once more the dignity of this holy Virgin, they may honour and venerate her with all affection of devotion, and own her as Queen and Mother. May her sweet name be lisped by the little ones, and linger on the lips of the aged and the dying; and may it be invoked by the afflicted, and hymned by the joyful; that this Star of the Sea being their protection and their guide, all may come to the harbour of eternal salvation. Who livest and reignest, world without end. Amen