Let $ABC$ be a triangle with $\angle BAC=60^\circ$. Consider a point $P$ inside the triangle having $PA=1$, $PB=2$ and $PC=3$. Find the maximum possible area of the triangle $ABC$.
1. **Fixing Point \( P \) and \( A \):**
   - Given \( P \) is inside the triangle \( ABC \) with \( PA = 1 \), \( PB = 2 \), and \( PC = 3 \).
   - The locus of \( B \) and \( C \) will be two circles centered at \( P \) with radii 2 and 3, respectively. Denote these circles as \(\omega_2\) and \(\omega_3\).

2. **Area of Triangle \( ABC \):**
   - The area of triangle \( ABC \) is given by:
     \[
     S_{ABC} = \frac{1}{2} \cdot b \cdot c \cdot \sin 60^\circ = \frac{\sqrt{3}}{4} \cdot b \cdot c
     \]
   - To maximize the area, we need to maximize the product \( b \cdot c \).

3. **Rotation and Collinearity:**
   - Rotate circle \(\omega_3\) about point \( A \) by \( 120^\circ \). Let the new circle be \(\omega_3'\).
   - After rotation, point \( C \) moves to \( C' \), and points \( B \), \( A \), and \( C' \) are collinear.

4. **Intersection of Circles:**
   - The problem now reduces to finding the line \(\ell\) passing through \( A \) that intersects circles \(\omega_2\) and \(\omega_3'\) at points \( P \) and \( Q \) such that \( AP \cdot AQ \) is maximized.

5. **Tangent Circle and Homothety:**
   - Consider a circle \((\mathcal{C})\) tangent to both \(\omega_2\) and \(\omega_3'\) with tangency points \( M \) and \( N \) such that \( A \), \( M \), and \( N \) are collinear.
   - For any points \( P \) and \( Q \) on \(\ell\) passing through \( A \), we have:
     \[
     AM \cdot AN \geq AP \cdot AQ
     \]
   - The circle \((\mathcal{C})\) can be constructed such that \( MN \) passes through the ex-homothety center of \(\omega_2\) and \(\omega_3'\).

6. **Maximizing the Area:**
   - The maximum product \( b \cdot c \) occurs when the line \(\ell\) is such that \( AP \cdot AQ \) is maximized.
   - Given the constraints, the maximum area of triangle \( ABC \) is achieved when \( b = 2 \) and \( c = 3 \).

7. **Calculating the Maximum Area:**
   - Substituting \( b = 2 \) and \( c = 3 \) into the area formula:
     \[
     S_{ABC} = \frac{\sqrt{3}}{4} \cdot 2 \cdot 3 = \frac{3\sqrt{3}}{2}
     \]

The final answer is \(\boxed{\frac{3\sqrt{3}}{2}}\)