Your question starts with the word 'can'. There's a big difference between that and 'should':
There is absolutely nothing in law which prevents any employer from sacking any employee at any time for any reason (or even in the complete absence of any reason). All that the law says is that certain types of dismissal are legally 'unfair', and that if an employee can convince an employment tribunal that he's been unfairly dismissed he is entitled to some form of recompense. (Even if a tribunal agrees that a dismissal is unfair the employee is still not automatically entitled to get his job back; the employer could opt to pay compensation instead).
So even if you've worked for an employer for 40 years, with exemplary service and not a single day off, he CAN sack you (but he'd be unwise to do so because of the compensation which a tribunal might award to you).
If you believe that you've been unfairly dismissed (and your employer won't listen to any representations from you or your union representative), all that you can do is to take the matter to a tribunal. That tribunal will then decide whether your employer's actions were legally 'fair' or not. However you need to be aware that tribunal hearings are held in public, with the more interesting ones appearing in the press. So you'd need to be prepared for your employer's accusations about your conduct to be known to everyone.
Chris