It's certainly no rumour. Text just sent round by BASSA:
"If U ring BA 4 work B4 next planned trip BA will ask U 2 come in 4 1 hr 2 sign no strike pledge. This is illegal. Plse refuse. We will take lgl advice."
Did they not think to take legal advice on this matter, that has been discussed on this thread for months, before tonight? Unbelievable.