Bad Yeast?

I made a partial grain ESB Saturday. Brewing went great. Put 3 gallons of wort into 2 gallons of water. Stirred it around real good to aerate it. SG: 1.054. Temp: 72 degrees. Everything went peachy.

I used a Wyeast 1028 London Ale Smack Pack. I smacked the pack about 4 hours before I pitched, it was good and inflated. Pitched it directly into the wort.

That was Saturday at about 2:30 PM. 49.5 hours later, I still have no visible fermentation or krausen. Bad Yeast? Time to repitch?

Any advice appreciated!

Have you given the primary a good shake yet since pitching (after the initial shake)? Shake it upppp!!!