Revere did warn the British
And again on the next day.
But let us follow Revere's adventures after his rousing of Hancock and Adams at the Clark house in his own language:
"After I had been there about half an hour Mr. Dawes arrived, who came from Boston, over the neck: we set off for Concord, & were overtaken by a young gentlemen named Prescot, who belonged to Concord, & was going home; when we had got about half way from Lexington to Concord, the other two, stopped at a house to awake the man, I kept along, when I had got about 200 yards of them; I saw two officers as before, I called to my company to come up, saying here was two of them (for I had told them what Mr. Devens told me, and of my being stoped) in an instant, I saw four of them, who rode up to me, with their pistols in their hands, said G____dd____n you stop if you go an inch further, you are a dead Man,' immeaditly Mr. Prescot came up we attempted to git thro them, but they kept before us, and swore if we did not turn into that pasture, they would blow our brains out, (they had placed themselves opposite to a pair of Barrs, and had taken the Barrs down) they forced us in, when we had got in, Mr. Precot said put on, He took to the left, I to the right towards a wood, at the bottom of the Pasture intending, when I gained that, to jump my Horse & run afoot.
Just as I reached it, out started six officers, seized my bridle, put their pistols to my Breast, ordered me to dismount, which I did: One of them, who appeared to have the command there, and much of a Gentleman, asked me where I came from; I told him, he asked what time I left it, I told him, he seemed surprised said Sr. may I have your name, I answered my name is Revere, what said he, Paul Revere; I answered yes; the others abused much, but he told me not to be afraid, no one should hurt me;
I told him they would miss their aim. He said they should not, they were only awaiting for some deserters they expected down the Road.
I told him I knew better, I knew what they were after; that I had alarmed the country all the way up, that their Boats were catch'd aground, and I should have 500 men there soon; one of them said they had 1,500 coming: he seemed surprised and rode off into the road, and informed them who took me, they came down immeaditly on a full gallop, one of them (whom I since learned was Major Mitchell of the 5th Reg.) Clap (doug d) his pistol to my head, and said he was going to ask me some questions, if I did not tell him the truth, he would blow my brains out.
http://www.earlyamerica.com/lives/revere/chapt1/Pat