For those interested in further information...
The Monarch Airbus ia an A321, G-OZBG, and I was the First Officer operating when the aircraft diverted into Heathrow on Tuesday night.
We had operated ex-Malaga, with the intended destination being Gatwick. When Gatwick's runway closed due to the snow, and with very few other UK airfields open, we ended up at Heathrow, landing at 22:56.
Having always wanted to fly into Heathrow, it was a little disappointing to only get visual with runway 09L as we crossed over the M25!