Coach Simon Davies was delighted with the Welsh win. "We had to compete against a big physical pack and the boys showed a lot of heart and courage to come back and win the game late on," he beamed.
"We took our chances against a very powerful French side added Davies" and our defence in the latter stages was outstanding, twice keeping the ball carrier up in our in-goal area."
Led by Tonyrefail CS and Blues North flanker Calum Thomas, Wales made light of the damp conditions early on with a fine opening try scored and converted by Williams.
The fly-half avoided tackles on half-way and on the opposition 22 to race in unopposed under the French posts.
France hit back with two penalties from their tricky little fly-half Otazo and it also took a great cover tackle by full-back Luke Treharne to deny wing Quentin Genest.
Centre Iolo Evans cut through only to spoil all the good work by delaying his pass and Wales went into the break just 10-9 ahead after the two fly-halves exchanged penalties.
Flimsy Welsh defence in the centre let centre Fabrice Catala put in the ever present Otaza for a try which the fly-half converted to make it 16-10 to the "jeunes tricolores"
Wales were under the cosh in the tight but when the chances came his way, Williams tied the scores with two well-struck penalties.
Back came France for that man Otazo to jink over for a try and just when it looked as if Wales would fail, up nipped scrum-half Lewis Jones to dash up the blind-side for a smart opportunist try.
A magnificent conversion from Williams edged Wales ahead but the drama was not over as Otazo had the chance to put over a winning penalty only to completely miss hit the ball with the last kick of the game.
WALES U16s Luke Treharne (St Michaels, Llanelli) (rep Ciaran Driscoll (St Cyres CS) 50); Harry Robinson (Radyr CS) (rep Gethin Hunter (Lampeter CS) 66), Iolo Evans (Ysgol Syr Hugh Owen, Caernarfon) (rep Matthew Roberts (Llantwit Major CS) 55), Thomas Pascoe (Cardinal Newman RCS), Nathan Brooks (Birchgrove CS); Lewis Williams (Tonyrefail CS), Lewis Jones (Ysgol Garth Olwg, Pontypridd); Darran Harris (Brecon HS) , Jack Dando (Porth CS) ( rep Jonathan Elley (Hawthorn HS) 54) Samson Lee (Coedcae CS), Jon Gardiner (Ysgol Bro Myrddin), Matthew Screech (Porth CS) (rep Jack Jones (Ysgol Gyfun Ystalyfera) 50), Richard Bloomfield (QEHS, Carmarthen) (rep Ellis Jenkins (Bryncelynnog CS) 50), Reuben Tucker (Cowbridge CS), Calum Thomas (Tonyrefail CS) (capt) (rep Will Thomas (Brynteg CS) 72)
FRANCE U16s Vincent Martin (Toulon) Bastien Fuster (La Rochelle) , Fabrice Catala (Colomiers), Emmanuel Husquin (Bourgoin), Quentin Genest Narbonne) (rep Yohan Atru (Montpellier) 50); Clement Otazo (Bayonne), Eric Esdcande (Montpellier) (capt) (rep Etienne Quinou (Haguenau) 66); Florian Fresia (Toulon) (rep Seb Taofifenau (Perpignan) 53), Jean-Charles Fidinde (Massy), Cherif Slimani (Stade Francais) (rep Cecillon Puleoto (Biarritz) 66, Pierre Gayraud (Perpignan), Andrew Chauveau (Begles-Bordeaux), Julin Kasubek (Clermont Auvergne), Karl Chateau (Orleans), Dan Malafosse (Brive) (rep Alban Placine (Pau) 50)
Referee: Filippo Bertelli (Italy)
Scorers: Wales U16s Tries: L Williams, L Jones; Cons: L Williams (2); Pens: L Williams (3)
France U16s Tries: L Otazo (2)' Cons: L Otazo; Pens: L Otazo (3)