The T is silent as in Harlow
Turning on the TV to find a weather forecast I caught a ten second clip of Rupert Everett talking about Byron's valet (I think). He pronounced the t in valet. Even the Americans don't do that. Maybe as he is several degrees posher than any of us that is why he did it. Just as we giggle at Septics when they lose the t on fillet, imagining they are showing continental sophistication, maybe the Norman classes here are reclaiming the t in valet and giggling at those not in the know.
I note the reference quoted below states such pronunciation to be considered ignorant or old-fashioned. I think I will risk being considered ignorant rather than being tarred with being considered modern or worse.
From now on I shall call my man a valet, with a t.
In English, the word is nowadays generally pronounced with a silent 't', as in French, the older pronunciation in which the 't' was pronounced (so 'valet' rhymes with 'pallet') being considered old-fashioned or even ignorant.
Fillet (pronounced “fill-it”)
(But Covert, as in the coat or the small wood every home should have to the north east, will remain T less.)