Halifax Bank Holiday scam

Vortigern

I've just received a statement for a Halifax ISA. I paid in this year's allowance on 6th April from a Halifax current account. This should be an instant transfer. The statement shows the transfer date as 10th April. Obviously 6th April was Good Friday and 10th April was the first banking day after the Easter weekend, but I still feel as though I've been robbed of just under £2 in interest. Of course £2 is not much, but I wonder how many times £2 the Halifax have saved by not paying interest on money which was quite clearly held by them on those holiday dates.

Have I been mugged?